document_title: Atom

question_text: who said all matter is made up of atoms

question_tokens: who said all matter is made up of atoms

text: Atom

text: History of atomic theory

text: Atoms in philosophy

text: The idea that matter is made up of discrete units is a very old idea, appearing in many ancient cultures such as Greece and India. The word "atom" was coined by the ancient Greek philosophers Leucippus and his pupil Democritus.[1][2] However, these ideas were founded in philosophical and theological reasoning rather than evidence and experimentation. As a result, their views on what atoms look like and how they behave were incorrect. They also could not convince everybody, so atomism was but one of a number of competing theories on the nature of matter. It was not until the 19th century that the idea was embraced and refined by scientists, when the blossoming science of chemistry produced discoveries that only the concept of atoms could explain.

text: First evidence-based theory

text: In the early 1800s, John Dalton used the concept of atoms to explain why elements always react in ratios of small whole numbers (the law of multiple proportions). For instance, there are two types of tin oxide: one is 88.1% tin and 11.9% oxygen and the other is 78.7% tin and 21.3% oxygen (tin(II) oxide and tin dioxide respectively). This means that 100g of tin will combine either with 13.5g or 27g of oxygen. 13.5 and 27 form a ratio of 1:2, a ratio of small whole numbers. This common pattern in chemistry suggested to Dalton that elements react in whole number multiples of discrete units—in other words, atoms. In the case of tin oxides, one tin atom will combine with either one or two oxygen atoms.[3]

text: Dalton also believed atomic theory could explain why water absorbs different gases in different proportions. For example, he found that water absorbs carbon dioxide far better than it absorbs nitrogen.[4] Dalton hypothesized this was due to the differences between the masses and configurations of the gases' respective particles, and carbon dioxide molecules (CO2) are heavier and larger than nitrogen molecules (N2).

text: Brownian motion

text: In 1827, botanist Robert Brown used a microscope to look at dust grains floating in water and discovered that they moved about erratically, a phenomenon that became known as "Brownian motion". This was thought to be caused by water molecules knocking the grains about. In 1905, Albert Einstein proved the reality of these molecules and their motions by producing the first Statistical physics analysis of Brownian motion.[5][6][7] French physicist Jean Perrin used Einstein's work to experimentally determine the mass and dimensions of atoms, thereby conclusively verifying Dalton's atomic theory.[8]

text: Discovery of the electron

text: The physicist J. J. Thomson measured the mass of cathode rays, showing they were made of particles, but were around 1800 times lighter than the lightest atom, hydrogen. Therefore, they were not atoms, but a new particle, the first subatomic particle to be discovered, which he originally called "corpuscle" but was later named electron, after particles postulated by George Johnstone Stoney in 1874. He also showed they were identical to particles given off by photoelectric and radioactive materials.[9] It was quickly recognized that they are the particles that carry electric currents in metal wires, and carry the negative electric charge within atoms. Thomson was given the 1906 Nobel Prize in Physics for this work. Thus he overturned the belief that atoms are the indivisible, ultimate particles of matter.[10] Thomson also incorrectly postulated that the low mass, negatively charged electrons were distributed throughout the atom in a uniform sea of positive charge. This became known as the plum pudding model.

text: Discovery of the nucleus

text: In 1909, Hans Geiger and Ernest Marsden, under the direction of Ernest Rutherford, bombarded a metal foil with alpha particles to observe how they scattered. They expected all the alpha particles to pass straight through with little deflection, because Thomson's model said that the charges in the atom are so diffuse that their electric fields could not affect the alpha particles much. However, Geiger and Marsden spotted alpha particles being deflected by angles greater than 90°, which was supposed to be impossible according to Thomson's model. To explain this, Rutherford proposed that the positive charge of the atom is concentrated in a tiny nucleus at the center of the atom.[11] Rutherford compared his findings to one firing a 15-inch shell at a sheet of tissue paper and it coming back to hit the person who fired it.[12]

text: Discovery of isotopes

text: While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table.[13] The term isotope was coined by Margaret Todd as a suitable name for different atoms that belong to the same element. J.J. Thomson created a technique for separating atom types through his work on ionized gases, which subsequently led to the discovery of stable isotopes.[14]

text: Bohr model

text: In 1913 the physicist Niels Bohr proposed a model in which the electrons of an atom were assumed to orbit the nucleus but could only do so in a finite set of orbits, and could jump between these orbits only in discrete changes of energy corresponding to absorption or radiation of a photon.[15] This quantization was used to explain why the electrons orbits are stable (given that normally, charges in acceleration, including circular motion, lose kinetic energy which is emitted as electromagnetic radiation, see synchrotron radiation) and why elements absorb and emit electromagnetic radiation in discrete spectra.[16]

text: Later in the same year Henry Moseley provided additional experimental evidence in favor of Niels Bohr's theory. These results refined Ernest Rutherford's and Antonius Van den Broek's model, which proposed that the atom contains in its nucleus a number of positive nuclear charges that is equal to its (atomic) number in the periodic table. Until these experiments, atomic number was not known to be a physical and experimental quantity. That it is equal to the atomic nuclear charge remains the accepted atomic model today.[17]

text: Chemical bonding explained

text: Chemical bonds between atoms were now explained, by Gilbert Newton Lewis in 1916, as the interactions between their constituent electrons.[18] As the chemical properties of the elements were known to largely repeat themselves according to the periodic law,[19] in 1919 the American chemist Irving Langmuir suggested that this could be explained if the electrons in an atom were connected or clustered in some manner. Groups of electrons were thought to occupy a set of electron shells about the nucleus.[20]

text: Further developments in quantum physics

text: The Stern–Gerlach experiment of 1922 provided further evidence of the quantum nature of atomic properties. When a beam of silver atoms was passed through a specially shaped magnetic field, the beam was split in a way correlated with the direction of an atom's angular momentum, or spin. As this spin direction is initially random, the beam would be expected to deflect in a random direction. Instead, the beam was split into two directional components, corresponding to the atomic spin being oriented up or down with respect to the magnetic field.[21]

text: In 1925 Werner Heisenberg published the first consistent mathematical formulation of quantum mechanics (Matrix Mechanics) [17]. One year earlier, in 1924, Louis de Broglie had proposed that all particles behave to an extent like waves and, in 1926, Erwin Schrödinger used this idea to develop a mathematical model of the atom (Wave Mechanics) that described the electrons as three-dimensional waveforms rather than point particles.

text: A consequence of using waveforms to describe particles is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at a given point in time; this became known as the uncertainty principle, formulated by Werner Heisenberg in 1927 [17]. In this concept, for a given accuracy in measuring a position one could only obtain a range of probable values for momentum, and vice versa.[22] This model was able to explain observations of atomic behavior that previous models could not, such as certain structural and spectral patterns of atoms larger than hydrogen. Thus, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed.[23][24]

text: Discovery of the neutron

text: The development of the mass spectrometer allowed the mass of atoms to be measured with increased accuracy. The device uses a magnet to bend the trajectory of a beam of ions, and the amount of deflection is determined by the ratio of an atom's mass to its charge. The chemist Francis William Aston used this instrument to show that isotopes had different masses. The atomic mass of these isotopes varied by integer amounts, called the whole number rule.[25] The explanation for these different isotopes awaited the discovery of the neutron, an uncharged particle with a mass similar to the proton, by the physicist James Chadwick in 1932. Isotopes were then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus.[26]

text: Fission, high-energy physics and condensed matter

text: In 1938, the German chemist Otto Hahn, a student of Rutherford, directed neutrons onto uranium atoms expecting to get transuranium elements. Instead, his chemical experiments showed barium as a product.[27][28] A year later, Lise Meitner and her nephew Otto Frisch verified that Hahn's result were the first experimental nuclear fission.[29][30] In 1944, Hahn received the Nobel prize in chemistry. Despite Hahn's efforts, the contributions of Meitner and Frisch were not recognized.[31]

text: In the 1950s, the development of improved particle accelerators and particle detectors allowed scientists to study the impacts of atoms moving at high energies.[32] Neutrons and protons were found to be hadrons, or composites of smaller particles called quarks. The standard model of particle physics was developed that so far has successfully explained the properties of the nucleus in terms of these sub-atomic particles and the forces that govern their interactions.[33]

text: Structure

text: Subatomic particles

text: Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton and the neutron; all three are fermions. However, the hydrogen-1 atom has no neutrons and the hydron ion has no electrons.

text: The electron is by far the least massive of these particles at 6969911000000000000♠9.11×10−31 kg, with a negative electrical charge and a size that is too small to be measured using available techniques.[34] It was the lightest particle with a positive rest mass measured, until the discovery of neutrino mass. Under ordinary conditions, electrons are bound to the positively charged nucleus by the attraction created from opposite electric charges. If an atom has more or fewer electrons than its atomic number, then it becomes respectively negatively or positively charged as a whole; a charged atom is called an ion. Electrons have been known since the late 19th century, mostly thanks to J.J. Thomson; see history of subatomic physics for details.

text: Protons have a positive charge and a mass 1,836 times that of the electron, at 6973167260000000000♠1.6726×10−27 kg. The number of protons in an atom is called its atomic number. Ernest Rutherford (1919) observed that nitrogen under alpha-particle bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it proton.

text: Neutrons have no electrical charge and have a free mass of 1,839 times the mass of the electron,[35] or 6973169290000000000♠1.6929×10−27 kg, the heaviest of the three constituent particles, but it can be reduced by the nuclear binding energy. Neutrons and protons (collectively known as nucleons) have comparable dimensions—on the order of 6985250000000000000♠2.5×10−15 m—although the 'surface' of these particles is not sharply defined.[36] The neutron was discovered in 1932 by the English physicist James Chadwick.

text: In the Standard Model of physics, electrons are truly elementary particles with no internal structure. However, both protons and neutrons are composite particles composed of elementary particles called quarks. There are two types of quarks in atoms, each having a fractional electric charge. Protons are composed of two up quarks (each with charge +2/3) and one down quark (with a charge of −1/3). Neutrons consist of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two particles.[37][38]

text: The quarks are held together by the strong interaction (or strong force), which is mediated by gluons. The protons and neutrons, in turn, are held to each other in the nucleus by the nuclear force, which is a residuum of the strong force that has somewhat different range-properties (see the article on the nuclear force for more). The gluon is a member of the family of gauge bosons, which are elementary particles that mediate physical forces.[37][38]

text: Nucleus

text: All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to 1.07 3√A fm, where A is the total number of nucleons.[39] This is much smaller than the radius of the atom, which is on the order of 105 fm. The nucleons are bound together by a short-ranged attractive potential called the residual strong force. At distances smaller than 2.5 fm this force is much more powerful than the electrostatic force that causes positively charged protons to repel each other.[40]

text: Atoms of the same element have the same number of protons, called the atomic number. Within a single element, the number of neutrons may vary, determining the isotope of that element. The total number of protons and neutrons determine the nuclide. The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay.[41]

text: The proton, the electron, and the neutron are classified as fermions. Fermions obey the Pauli exclusion principle which prohibits identical fermions, such as multiple protons, from occupying the same quantum state at the same time. Thus, every proton in the nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and to all electrons of the electron cloud. However, a proton and a neutron are allowed to occupy the same quantum state.[42]

text: For atoms with low atomic numbers, a nucleus that has more neutrons than protons tends to drop to a lower energy state through radioactive decay so that the neutron–proton ratio is closer to one. However, as the atomic number increases, a higher proportion of neutrons is required to offset the mutual repulsion of the protons. Thus, there are no stable nuclei with equal proton and neutron numbers above atomic number Z = 20 (calcium) and as Z increases, the neutron–proton ratio of stable isotopes increases.[42] The stable isotope with the highest proton–neutron ratio is lead-208 (about 1.5).

text: The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at the core of the Sun protons require energies of 3–10 keV to overcome their mutual repulsion—the coulomb barrier—and fuse together into a single nucleus.[43] Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay. The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies the number of protons in a nucleus, the atom changes to a different chemical element.[44][45]

text: If the mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate particles, then the difference between these two values can be emitted as a type of usable energy (such as a gamma ray, or the kinetic energy of a beta particle), as described by Albert Einstein's mass–energy equivalence formula, E = mc2, where m is the mass loss and c is the speed of light. This deficit is part of the binding energy of the new nucleus, and it is the non-recoverable loss of the energy that causes the fused particles to remain together in a state that requires this energy to separate.[46]

text: The fusion of two nuclei that create larger nuclei with lower atomic numbers than iron and nickel—a total nucleon number of about 60—is usually an exothermic process that releases more energy than is required to bring them together.[47] It is this energy-releasing process that makes nuclear fusion in stars a self-sustaining reaction. For heavier nuclei, the binding energy per nucleon in the nucleus begins to decrease. That means fusion processes producing nuclei that have atomic numbers higher than about 26, and atomic masses higher than about 60, is an endothermic process. These more massive nuclei can not undergo an energy-producing fusion reaction that can sustain the hydrostatic equilibrium of a star.[42]

text: Electron cloud

text: The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed for the electron to escape. The closer an electron is to the nucleus, the greater the attractive force. Hence electrons bound near the center of the potential well require more energy to escape than those at greater separations.

text: Electrons, like other particles, have properties of both a particle and a wave. The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave—a wave form that does not move relative to the nucleus. This behavior is defined by an atomic orbital, a mathematical function that characterises the probability that an electron appears to be at a particular location when its position is measured.[48] Only a discrete (or quantized) set of these orbitals exist around the nucleus, as other possible wave patterns rapidly decay into a more stable form.[49] Orbitals can have one or more ring or node structures, and differ from each other in size, shape and orientation.[50]

text: Each atomic orbital corresponds to a particular energy level of the electron. The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. Likewise, through spontaneous emission, an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. These characteristic energy values, defined by the differences in the energies of the quantum states, are responsible for atomic spectral lines.[49]

text: The amount of energy needed to remove or add an electron—the electron binding energy—is far less than the binding energy of nucleons. For example, it requires only 13.6 eV to strip a ground-state electron from a hydrogen atom,[51] compared to 2.23 million eV for splitting a deuterium nucleus.[52] Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either a deficit or a surplus of electrons are called ions. Electrons that are farthest from the nucleus may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals.[53]

text: Properties

text: Nuclear properties

text: By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form,[54] also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single proton element hydrogen up to the 118-proton element oganesson.[55] All known isotopes of elements with atomic numbers greater than 82 are radioactive, although the radioactivity of element 83 (bismuth) is so slight as to be practically negligible.[56][57]

text: About 339 nuclides occur naturally on Earth,[58] of which 254 (about 75%) have not been observed to decay, and are referred to as "stable isotopes". However, only 90 of these nuclides are stable to all decay, even in theory. Another 164 (bringing the total to 254) have not been observed to decay, even though in theory it is energetically possible. These are also formally classified as "stable". An additional 34 radioactive nuclides have half-lives longer than 80 million years, and are long-lived enough to be present from the birth of the solar system. This collection of 288 nuclides are known as primordial nuclides. Finally, an additional 51 short-lived nuclides are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium), or else as products of natural energetic processes on Earth, such as cosmic ray bombardment (for example, carbon-14).[59][note 1]

text: For 80 of the chemical elements, at least one stable isotope exists. As a rule, there is only a handful of stable isotopes for each of these elements, the average being 3.2 stable isotopes per element. Twenty-six elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin. Elements 43, 61, and all elements numbered 83 or higher have no stable isotopes.[60][page needed]

text: Stability of isotopes is affected by the ratio of protons to neutrons, and also by the presence of certain "magic numbers" of neutrons or protons that represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus; filled shells, such as the filled shell of 50 protons for tin, confers unusual stability on the nuclide. Of the 254 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: hydrogen-2 (deuterium), lithium-6, boron-10 and nitrogen-14. Also, only four naturally occurring, radioactive odd–odd nuclides have a half-life over a billion years: potassium-40, vanadium-50, lanthanum-138 and tantalum-180m. Most odd–odd nuclei are highly unstable with respect to beta decay, because the decay products are even–even, and are therefore more strongly bound, due to nuclear pairing effects.[60][page needed]

text: Mass

text: The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons).

text: The actual mass of an atom at rest is often expressed using the unified atomic mass unit (u), also called dalton (Da). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately 6973166000000000000♠1.66×10−27 kg.[61] Hydrogen-1 (the lightest isotope of hydrogen which is also the nuclide with the lowest mass) has an atomic weight of 1.007825 u.[62] The value of this number is called the atomic mass. A given atom has an atomic mass approximately equal (within 1%) to its mass number times the atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 u). However, this number will not be exactly an integer except in the case of carbon-12 (see below).[63] The heaviest stable atom is lead-208,[56] with a mass of 7002207976652100000♠207.9766521 u.[64]

text: As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles. One mole of atoms of any element always has the same number of atoms (about 7023602200000000000♠6.022×1023). This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element has a mass close to one gram. Because of the definition of the unified atomic mass unit, each carbon-12 atom has an atomic mass of exactly 12 u, and so a mole of carbon-12 atoms weighs exactly 0.012 kg.[61]

text: Shape and size

text: Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus.[65] However, this assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Atomic radii may be derived from the distances between two nuclei when the two atoms are joined in a chemical bond. The radius varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighboring atoms (coordination number) and a quantum mechanical property known as spin.[66] On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right).[67] Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm.[68]

text: When subjected to external forces, like electrical fields, the shape of an atom may deviate from spherical symmetry. The deformation depends on the field magnitude and the orbital type of outer shell electrons, as shown by group-theoretical considerations. Aspherical deviations might be elicited for instance in crystals, where large crystal-electrical fields may occur at low-symmetry lattice sites.[69][70] Significant ellipsoidal deformations have been shown to occur for sulfur ions[71] and chalcogen ions[72] in pyrite-type compounds.

text: Atomic dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they cannot be viewed using an optical microscope. However, individual atoms can be observed using a scanning tunneling microscope. To visualize the minuteness of the atom, consider that a typical human hair is about 1 million carbon atoms in width.[73] A single drop of water contains about 2 sextillion (7021200000000000000♠2×1021) atoms of oxygen, and twice the number of hydrogen atoms.[74] A single carat diamond with a mass of 6996200000000000000♠2×10−4 kg contains about 10 sextillion (1022) atoms of carbon.[note 2] If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple.[75]

text: Radioactive decay

text: Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force, which only acts over distances on the order of 1 fm.[76]

text: The most common forms of radioactive decay are:[77][78]

text:
Alpha decay: this process is caused when the nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. The result of the emission is a new element with a lower atomic number.
Beta decay (and electron capture): these processes are regulated by the weak force, and result from a transformation of a neutron into a proton, or a proton into a neutron. The neutron to proton transition is accompanied by the emission of an electron and an antineutrino, while proton to neutron transition (except in electron capture) causes the emission of a positron and a neutrino. The electron or positron emissions are called beta particles. Beta decay either increases or decreases the atomic number of the nucleus by one. Electron capture is more common than positron emission, because it requires less energy. In this type of decay, an electron is absorbed by the nucleus, rather than a positron emitted from the nucleus. A neutrino is still emitted in this process, and a proton changes to a neutron.
Gamma decay: this process results from a change in the energy level of the nucleus to a lower state, resulting in the emission of electromagnetic radiation. The excited state of a nucleus which results in gamma emission usually occurs following the emission of an alpha or a beta particle. Thus, gamma decay usually follows alpha or beta decay.

text: Other more rare types of radioactive decay include ejection of neutrons or protons or clusters of nucleons from a nucleus, or more than one beta particle. An analog of gamma emission which allows excited nuclei to lose energy in a different way, is internal conversion—a process that produces high-speed electrons that are not beta rays, followed by production of high-energy photons that are not gamma rays. A few large nuclei explode into two or more charged fragments of varying masses plus several neutrons, in a decay called spontaneous nuclear fission.

text: Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth.[76]

text: Magnetic moment

text: Elementary particles possess an intrinsic quantum mechanical property known as spin. This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be rotating. Spin is measured in units of the reduced Planck constant (ħ), with electrons, protons and neutrons all having spin ½ ħ, or "spin-½". In an atom, electrons in motion around the nucleus possess orbital angular momentum in addition to their spin, while the nucleus itself possesses angular momentum due to its nuclear spin.[79]

text: The magnetic field produced by an atom—its magnetic moment—is determined by these various forms of angular momentum, just as a rotating charged object classically produces a magnetic field. However, the most dominant contribution comes from electron spin. Due to the nature of electrons to obey the Pauli exclusion principle, in which no two electrons may be found in the same quantum state, bound electrons pair up with each other, with one member of each pair in a spin up state and the other in the opposite, spin down state. Thus these spins cancel each other out, reducing the total magnetic dipole moment to zero in some atoms with even number of electrons.[80]

text: In ferromagnetic elements such as iron, cobalt and nickel, an odd number of electrons leads to an unpaired electron and a net overall magnetic moment. The orbitals of neighboring atoms overlap and a lower energy state is achieved when the spins of unpaired electrons are aligned with each other, a spontaneous process known as an exchange interaction. When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field. Paramagnetic materials have atoms with magnetic moments that line up in random directions when no magnetic field is present, but the magnetic moments of the individual atoms line up in the presence of a field.[80][81]

text: The nucleus of an atom will have no spin when it has even numbers of both neutrons and protons, but for other cases of odd numbers, the nucleus may have a spin. Normally nuclei with spin are aligned in random directions because of thermal equilibrium. However, for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction—a condition called hyperpolarization. This has important applications in magnetic resonance imaging.[82][83]

text: Energy levels

text: The potential energy of an electron in an atom is negative, its dependence of its position reaches the minimum (the most absolute value) inside the nucleus, and vanishes when the distance from the nucleus goes to infinity, roughly in an inverse proportion to the distance. In the quantum-mechanical model, a bound electron can only occupy a set of states centered on the nucleus, and each state corresponds to a specific energy level; see time-independent Schrödinger equation for theoretical explanation. An energy level can be measured by the amount of energy needed to unbind the electron from the atom, and is usually given in units of electronvolts (eV). The lowest energy state of a bound electron is called the ground state, i.e. stationary state, while an electron transition to a higher level results in an excited state.[84] The electron's energy raises when n increases because the (average) distance to the nucleus increases. Dependence of the energy on ℓ is caused not by electrostatic potential of the nucleus, but by interaction between electrons.

text: For an electron to transition between two different states, e.g. grounded state to first excited level (ionization), it must absorb or emit a photon at an energy matching the difference in the potential energy of those levels, according to Niels Bohr model, what can be precisely calculated by the Schrödinger equation. Electrons jump between orbitals in a particle-like fashion. For example, if a single photon strikes the electrons, only a single electron changes states in response to the photon; see Electron properties.

text: The energy of an emitted photon is proportional to its frequency, so these specific energy levels appear as distinct bands in the electromagnetic spectrum.[85] Each element has a characteristic spectrum that can depend on the nuclear charge, subshells filled by electrons, the electromagnetic interactions between the electrons and other factors.[86]

text: When a continuous spectrum of energy is passed through a gas or plasma, some of the photons are absorbed by atoms, causing electrons to change their energy level. Those excited electrons that remain bound to their atom spontaneously emit this energy as a photon, traveling in a random direction, and so drop back to lower energy levels. Thus the atoms behave like a filter that forms a series of dark absorption bands in the energy output. (An observer viewing the atoms from a view that does not include the continuous spectrum in the background, instead sees a series of emission lines from the photons emitted by the atoms.) Spectroscopic measurements of the strength and width of atomic spectral lines allow the composition and physical properties of a substance to be determined.[87]

text: Close examination of the spectral lines reveals that some display a fine structure splitting. This occurs because of spin–orbit coupling, which is an interaction between the spin and motion of the outermost electron.[88] When an atom is in an external magnetic field, spectral lines become split into three or more components; a phenomenon called the Zeeman effect. This is caused by the interaction of the magnetic field with the magnetic moment of the atom and its electrons. Some atoms can have multiple electron configurations with the same energy level, which thus appear as a single spectral line. The interaction of the magnetic field with the atom shifts these electron configurations to slightly different energy levels, resulting in multiple spectral lines.[89] The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenomenon called the Stark effect.[90]

text: If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level. For this to occur, the electron must drop to a lower energy state that has an energy difference matching the energy of the interacting photon. The emitted photon and the interacting photon then move off in parallel and with matching phases. That is, the wave patterns of the two photons are synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band.[91]

text: Valence and bonding behavior

text: Valency is the combining power of an element. It is equal to number of hydrogen atoms that atom can combine or displace in forming compounds.[92] The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in that shell are called valence electrons. The number of valence electrons determines the bonding behavior with other atoms. Atoms tend to chemically react with each other in a manner that fills (or empties) their outer valence shells.[93] For example, a transfer of a single electron between atoms is a useful approximation for bonds that form between atoms with one-electron more than a filled shell, and others that are one-electron short of a full shell, such as occurs in the compound sodium chloride and other chemical ionic salts. However, many elements display multiple valences, or tendencies to share differing numbers of electrons in different compounds. Thus, chemical bonding between these elements takes many forms of electron-sharing that are more than simple electron transfers. Examples include the element carbon and the organic compounds.[94]

text: The chemical elements are often displayed in a periodic table that is laid out to display recurring chemical properties, and elements with the same number of valence electrons form a group that is aligned in the same column of the table. (The horizontal rows correspond to the filling of a quantum shell of electrons.) The elements at the far right of the table have their outer shell completely filled with electrons, which results in chemically inert elements known as the noble gases.[95][96]

text: States

text: Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. By varying the conditions, materials can transition between solids, liquids, gases and plasmas.[97] Within a state, a material can also exist in different allotropes. An example of this is solid carbon, which can exist as graphite or diamond.[98] Gaseous allotropes exist as well, such as dioxygen and ozone.

text: At temperatures close to absolute zero, atoms can form a Bose–Einstein condensate, at which point quantum mechanical effects, which are normally only observed at the atomic scale, become apparent on a macroscopic scale.[99][100] This super-cooled collection of atoms then behaves as a single super atom, which may allow fundamental checks of quantum mechanical behavior.[101]

text: Identification

text: The scanning tunneling microscope is a device for viewing surfaces at the atomic level. It uses the quantum tunneling phenomenon, which allows particles to pass through a barrier that would normally be insurmountable. Electrons tunnel through the vacuum between two planar metal electrodes, on each of which is an adsorbed atom, providing a tunneling-current density that can be measured. Scanning one atom (taken as the tip) as it moves past the other (the sample) permits plotting of tip displacement versus lateral separation for a constant current. The calculation shows the extent to which scanning-tunneling-microscope images of an individual atom are visible. It confirms that for low bias, the microscope images the space-averaged dimensions of the electron orbitals across closely packed energy levels—the Fermi level local density of states.[102][103]

text: An atom can be ionized by removing one of its electrons. The electric charge causes the trajectory of an atom to bend when it passes through a magnetic field. The radius by which the trajectory of a moving ion is turned by the magnetic field is determined by the mass of the atom. The mass spectrometer uses this principle to measure the mass-to-charge ratio of ions. If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope in the sample by measuring the intensity of the different beams of ions. Techniques to vaporize atoms include inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry, both of which use a plasma to vaporize samples for analysis.[104]

text: A more area-selective method is electron energy loss spectroscopy, which measures the energy loss of an electron beam within a transmission electron microscope when it interacts with a portion of a sample. The atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-flight mass spectrometry.[105]

text: Spectra of excited states can be used to analyze the atomic composition of distant stars. Specific light wavelengths contained in the observed light from stars can be separated out and related to the quantized transitions in free gas atoms. These colors can be replicated using a gas-discharge lamp containing the same element.[106] Helium was discovered in this way in the spectrum of the Sun 23 years before it was found on Earth.[107]

text: Origin and current state

text: Atoms form about 4% of the total energy density of the observable Universe, with an average density of about 0.25 atoms/m3.[108] Within a galaxy such as the Milky Way, atoms have a much higher concentration, with the density of matter in the interstellar medium (ISM) ranging from 105 to 109 atoms/m3.[109] The Sun is believed to be inside the Local Bubble, a region of highly ionized gas, so the density in the solar neighborhood is only about 103 atoms/m3.[110] Stars form from dense clouds in the ISM, and the evolutionary processes of stars result in the steady enrichment of the ISM with elements more massive than hydrogen and helium. Up to 95% of the Milky Way's atoms are concentrated inside stars and the total mass of atoms forms about 10% of the mass of the galaxy.[111] (The remainder of the mass is an unknown dark matter.)[112]

text: Formation

text: Electrons are thought to exist in the Universe since early stages of the Big Bang. Atomic nuclei forms in nucleosynthesis reactions. In about three minutes Big Bang nucleosynthesis produced most of the helium, lithium, and deuterium in the Universe, and perhaps some of the beryllium and boron.[113][114][115]

text: Ubiquitousness and stability of atoms relies on their binding energy, which means that an atom has a lower energy than an unbound system of the nucleus and electrons. Where the temperature is much higher than ionization potential, the matter exists in the form of plasma—a gas of positively charged ions (possibly, bare nuclei) and electrons. When the temperature drops below the ionization potential, atoms become statistically favorable. Atoms (complete with bound electrons) became to dominate over charged particles 380,000 years after the Big Bang—an epoch called recombination, when the expanding Universe cooled enough to allow electrons to become attached to nuclei.[116]

text: Since the Big Bang, which produced no carbon or heavier elements, atomic nuclei have been combined in stars through the process of nuclear fusion to produce more of the element helium, and (via the triple alpha process) the sequence of elements from carbon up to iron;[117] see stellar nucleosynthesis for details.

text: Isotopes such as lithium-6, as well as some beryllium and boron are generated in space through cosmic ray spallation.[118] This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected.

text: Elements heavier than iron were produced in supernovae through the r-process and in AGB stars through the s-process, both of which involve the capture of neutrons by atomic nuclei.[119] Elements such as lead formed largely through the radioactive decay of heavier elements.[120]

text: Earth

text: Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine the age of the Earth through radiometric dating.[121][122] Most of the helium in the crust of the Earth (about 99% of the helium from gas wells, as shown by its lower abundance of helium-3) is a product of alpha decay.[123]

text: There are a few trace atoms on Earth that were not present at the beginning (i.e., not "primordial"), nor are results of radioactive decay. Carbon-14 is continuously generated by cosmic rays in the atmosphere.[124] Some atoms on Earth have been artificially generated either deliberately or as by-products of nuclear reactors or explosions.[125][126] Of the transuranic elements—those with atomic numbers greater than 92—only plutonium and neptunium occur naturally on Earth.[127][128] Transuranic elements have radioactive lifetimes shorter than the current age of the Earth[129] and thus identifiable quantities of these elements have long since decayed, with the exception of traces of plutonium-244 possibly deposited by cosmic dust.[121] Natural deposits of plutonium and neptunium are produced by neutron capture in uranium ore.[130]

text: The Earth contains approximately 7050133000000000000♠1.33×1050 atoms.[131] Although small numbers of independent atoms of noble gases exist, such as argon, neon, and helium, 99% of the atmosphere is bound in the form of molecules, including carbon dioxide and diatomic oxygen and nitrogen. At the surface of the Earth, an overwhelming majority of atoms combine to form various compounds, including water, salt, silicates and oxides. Atoms can also combine to create materials that do not consist of discrete molecules, including crystals and liquid or solid metals.[132][133] This atomic matter forms networked arrangements that lack the particular type of small-scale interrupted order associated with molecular matter.[134]

text: Rare and theoretical forms

text: Superheavy elements

text: While isotopes with atomic numbers higher than lead (82) are known to be radioactive, an "island of stability" has been proposed for some elements with atomic numbers above 103. These superheavy elements may have a nucleus that is relatively stable against radioactive decay.[135] The most likely candidate for a stable superheavy atom, unbihexium, has 126 protons and 184 neutrons.[136]

text: Exotic matter

text: Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. When a matter and corresponding antimatter particle meet, they annihilate each other. Because of this, along with an imbalance between the number of matter and antimatter particles, the latter are rare in the universe. The first causes of this imbalance are not yet fully understood, although theories of baryogenesis may offer an explanation. As a result, no antimatter atoms have been discovered in nature.[137][138] However, in 1996 the antimatter counterpart of the hydrogen atom (antihydrogen) was synthesized at the CERN laboratory in Geneva.[139][140]

text: Other exotic atoms have been created by replacing one of the protons, neutrons or electrons with other particles that have the same charge. For example, an electron can be replaced by a more massive muon, forming a muonic atom. These types of atoms can be used to test the fundamental predictions of physics.[141][142][143]


document_title: Designated Survivor (season 2)

question_text: who plays the cdc doctor on designated survivor

root

text: Designated Survivor (season 2)

text: Overview[edit]

text: One year into office, President Thomas Kirkman juggles searching for the mastermind behind the attack on the Capitol Building, dealing with the day-to-day situations that take place at home and abroad, and helping a nation rebuild.

tag: p

text: Cast and characters[edit]

text: Main[edit]

text:
Kiefer Sutherland as President Thomas "Tom" Kirkman[3]
Natascha McElhone as First Lady Alexandra "Alex" Kirkman[3]
Paulo Costanzo as White House Political Director Lyor Boone[3]
Adan Canto as National Security Advisor Aaron Shore[3]
Italia Ricci as White House Chief of Staff Emily Rhodes[3]
LaMonica Garrett as Mike Ritter[3]
Zoe McLellan as White House Counsel Kendra Daynes[3]
Ben Lawson as Damian Rennett[3]
Kal Penn as White House Press Secretary Seth Wright[3]
Maggie Q as Hannah Wells[3]

tag: ul

text: Recurring[edit]

text:
Terry Serpico as Patrick Lloyd
Jake Epstein as Chuck Russink
Mckenna Grace as Penny Kirkman
Bonnie Bedelia as Eva Booker
Reed Diamond as John Forstell
Geoff Pierson as Cornelius Moss
Mykelti Williamson as Admiral Chernow
Breckin Meyer as Trey Kirkman[4]

text: Episodes[edit]

text:
No.
overall
No. in
season
Title
Directed by
Written by
Original air date
U.S. viewers
(millions)

22
1
"One Year In"
Chris Grismer
Keith Eisner
September 27, 2017 (2017-09-27)
5.50[5]

Kirkman struggles to prevent a possible international crisis when Ukrainian separatists hijack a Russian airplane with American citizens among the passengers; Wells works with MI6 agent Damian Rennett (Ben Lawson) to find the Capitol bombing's chief architect; Emily juggles hiring political consultant Lyor Boone (Paulo Costanzo) and determining where Seth's loyalties lie; the senior staff attempts to keep a visiting writer occupied before his audience with the President.

23
2
"Sting of the Tail"
Frederick E. O. Toye
Keith Eisner
October 4, 2017 (2017-10-04)
4.80[6]

Kirkman works with Wells and Rennett when Patrick Lloyd (Terry Serpico) reemerges and threatens to unleash sarin gas on the D.C. metropolitan area if his demands are not met; Seth struggles to finish Kirkman's speech for the Correspondents' Dinner; the senior staff welcomes White House Counsel Kendra Daynes (Zoe McLellan) into the fold.

24
3
"Outbreak"
Chris Grismer
Ashley Gable
October 11, 2017 (2017-10-11)
4.61[7]

Kirkman works with the CDC to contain a deadly viral outbreak; Wells and Rennett dig deeper into Patrick Lloyd's motives; Kendra attempts to settle a debate about a controversial Confederate statue; the senior staff prepares for the presentation of an Amazonian frog named after the President.

25
4
"Equilibrium"
Joe Lazarov
Paul Redford & Keith Eisner
October 18, 2017 (2017-10-18)
4.34[8]

Kirkman and the senior staff attempt to resolve a border dispute between the United States and Mexico; Wells interrogates Alex about her mother's possible involvement in a decades-old crime; an investigator from the Office of Management and Budget tries to determine who is responsible for breaking a priceless vase.

26
5
"Suckers"
Fred Gerber
Bill Chais
October 25, 2017 (2017-10-25)
3.94[9]

Kirkman and the senior staff work together to regain the general public's trust after a private conversation is taken out of context on national television; Wells and Rennett reunite when a visiting British MP is gunned down; Alex becomes emotionally involved in the ongoing investigation against her mother.

27
6
"Two Ships"
Leslie Libman
Jessica Grasl
November 1, 2017 (2017-11-01)
3.92[10]

Kirkman sets out to prevent a potential national security threat after a stranded U.S. Navy ship with a state-of-the-art surveillance system drifts into enemy waters; Wells and Rennett continue investigating Charlotte Thorne's death; Kendra tries to convince Alex's mother to make a difficult decision; Emily reunites with her absentee father.

28
7
"Family Ties"
Milan Cheylov
Pierluigi Cothran
November 15, 2017 (2017-11-15)
4.05[11]

The First Family struggles to prevent a scandal when Leo is sued by a man protesting a Turkish activist; Alex finds herself caught in the middle of a murder investigation; Secretary Moss stonewalls Wells and Rennett as they investigate his relationship with Charlotte Thorne.

29
8
"Home"
Ian Toynton
Pat Cunnane
November 29, 2017 (2017-11-29)
4.03[12]

During a secret trip to Afghanistan, Kirkman negotiates with influential warlords and Wells comes under fire. Back home, Seth lands in legal trouble, while trying to protect his younger brother. The charges were eventually quashed by Daynes.

30
9
"Three-Letter Day"
Jeannot Szwarc
Bill Chais & Ashley Arena
December 6, 2017 (2017-12-06)
3.91[13]

Kirkman dispatches his staff to investigate a war hero's legacy, a man on death row and a bee colony's collapse. Wells follows a trail of dirty money.

31
10
"Line of Fire"
Chris Grismer
Keith Eisner
December 13, 2017 (2017-12-13)
4.39[14]

Religious zealots in the path of a raging fire square off with the White House over their convictions and a member's baby daughter's life-threatening condition. Wells digs for the truth behind a betrayal. Kirkman reinstates the D.C. medical license of a controversial surgeon whose pioneering work with artificial blood could resolve the standoff between the zealots and the administration. Alex's victory over the DOJ investigation carries a tragic price.

32
11
TBA
TBA
TBA
February 28, 2018 (2018-02-28)
TBD

tag: table

text: Production[edit]

text: Designated Survivor was renewed for a second season on May 11, 2017. Former The Good Wife executive producer Keith Eisner will take over as showrunner for the second season.[15] Eisner will be the fourth showrunner for the show, replacing Jeff Melvoin, who was hired as showrunner in December 2016, taking over for Jon Harmon Feldman.[16] The show's original showrunner Amy B. Harris stepped down due to creative differences after the series' official pickup in February 2016.[17]

text: On June 22, 2017, cast member Virginia Madsen announced that she would not be returning for the second season as Kimble Hookstraten as she commented "I guess they had other stories to tell. It's a big show so I wish them well."[18] After the first season finale, Sutherland announced that the show would add three new characters for the second season. Two of the character descriptions was "a “fiery” female White House Counsel and a “ruggedly handsome” MI6 operative who crosses paths with Hannah."[19] TVLine announced on June 29, 2017, that Paulo Costanzo had been cast as a series regular role as Lyor Boone, the new White House Political Director.[20] Deadline reported on July 17, 2017, that Ben Lawson had been cast as the series regular character Damian Rennett, an MI-6 operative.[21]

text: Ratings[edit]

text:
No.
Title
Air date
Rating/share
(18–49)
Viewers
(millions)
DVR
(18–49)
DVR viewers
(millions)
Total
(18–49)
Total viewers
(millions)

1
"One Year In"
September 27, 2017
1.1/4
5.50[5]
1.4
5.84
2.5
11.34[22]

2
"Sting of the Tail"
October 4, 2017
0.9/4
4.80[6]
1.2
5.20
2.1
10.00[23]

3
"Outbreak"
October 11, 2017
0.9/4
4.61[7]
1.1
5.07
2.0
9.68[24]

4
"Equilibrium"
October 18, 2017
0.8/3
4.34[8]
1.1
5.00
1.9
9.34[25]

5
"Suckers"
October 25, 2017
0.7/3
3.94[9]
1.0
4.60
1.7
8.54[26]

6
"Two Ships"
November 1, 2017
0.7/3
3.92[10]
0.9
4.31
1.6
8.23[27]

7
"Family Ties"
November 15, 2017
0.8/3
4.05[11]
0.9
4.47
1.7
8.52[28]

8
"Home"
November 29, 2017
0.7/3
4.03[12]
1.0
4.83
1.7
8.86[29]

9
"Three-Letter Day"
December 6, 2017
0.7/3
3.87[13]
N/A
N/A
N/A
N/A

10
"Line of Fire"
December 13, 2017
0.8/3
4.38[14]
N/A
N/A
N/A
N/A


document_title: Pandora (jewelry)

question_text: 6. what is the name of the danish goldsmith who founded the pandora jewelry company

question_tokens: 6 . what is the name of the danish goldsmith who founded the pandora jewelry company

text: Pandora (jewelry)

text: History[edit]

text:
Pandora was founded in 1982[citation needed] by Danish goldsmith Per Enevoldsen and his then wife Winnie Enevoldsen. The pair began on a small scale by importing jewellery from Thailand and selling to consumers.[2]
After a successful wholesale venture, in 1989 Enevoldsen hired in-house designers and established a manufacturing site in Thailand, where it is still located. With low production costs and an efficient supply chain, the Enevoldsens could provide affordable, hand-finished jewellery for the mass market. Pandora's collection grew to include an assortment of rings, necklaces, earrings and watches.  Pandora started selling its signature bracelets in 2000 after a patent and several years of development.[3]

text: The Danish private equity group Axcel bought a 60% stake in the company from the Enevoldsen family in 2008. Shares totalling DKK 9.96 billion (US$ 1.84 billion) were sold in an IPO in October 2010, one of the biggest IPOs in Europe that year, giving Pandora a market capitalisation of around DKK 27 billion.[4] The company is publicly listed on the NASDAQ OMX Copenhagen Stock Exchange in Denmark and is a component of the OMX Copenhagen 20 index.

text: Pandora became the world's third-largest jewellery company in terms of sales, after Cartier and Tiffany & Co.[2] In 2011, more than one piece of Pandora jewellery was sold every second on average.[5] Shares fell nearly 80% in 2011 after a shift in focus to higher-end designs alienated core customers, but performance recovered after a return to the more affordable mass market, with the group reporting revenue of DKK 11.9 billion and net profit in excess of DKK 3 billion in 2014.[6]

text: Distribution network[edit]

text:
Sales of the Pandora brand began in Europe and it first entered North America in 2003. The company opened concept stores around the world before its franchising model began in Australia in 2009.[5]
Pandora products are sold in more than 100 countries on six continents through approximately 7,700 points of sale, including approximately 2,200 concept stores.[7] The company employs over 22,300 people, of whom 13,200 are located in Gemopolis, Thailand, the company's sole manufacturing site since 1989.[8]

text: Pandora launched an online sales platform in Europe in 2011, and began working to expand its e-commerce to the majority of its markets including Australia.[9]

text: Europe and the United States accounted for nearly 90% of group sales in 2014. The group announced a Chinese distribution deal in 2015, with plans to increase store numbers to "a couple of hundred" in China.[6] In 2015, it bought out Oracle Investment's shares in its Chinese distribution service.[10]


document_title: List of countries by oil production

question_text: which country is second to opec in terms of oil production

text: List of countries by oil production

text: This is a list of countries by oil production, as compiled from the U.S. Energy Information Administration database for calendar year 2016, tabulating all countries on a comparable best-estimate basis. Compared with shorter-term data, the full-year figures are less prone to distortion from periodic maintenance shutdowns and other seasonal cycles. The volumes in the table represent crude oil and lease condensate, the hydrocarbon liquids collected at or near the wellhead. The volumes in the table do not include biofuel. They also do not include the increase in liquid volumes during oil refining ("refinery gain"), or liquids separated from natural gas in gas processing plants (natural gas liquids).[1]

text: Under this definition, total world oil production in 2016 averaged 80,622,000 barrels per day. Approximately 68% came from the top ten countries, and an overlapping 44% came from the fourteen current OPEC members, highlighted with blue shading in the table below.

text: For many years, the top three producers have been (alphabetically) Russia, Saudi Arabia, and the United States. Each of these countries experienced major production declines at different times in the past, but since 2014 all three have been producing near their peak rates of 9 to 11 million barrels per day.[2]

text:
Country
Oil Production
(bbl/day, 2016)[1]

1
 Russia
10,551,497

2
 Saudi Arabia (OPEC)
10,460,710

3
 United States
8,875,817

4
 Iraq (OPEC)
4,451,516

5
 Iran (OPEC)
3,990,956

6
 China
3,980,650

7
 Canada
3,662,694

8
 United Arab Emirates (OPEC)
3,106,077

9
 Kuwait (OPEC)
2,923,825

10
 Brazil
2,515,459

11
 Venezuela (OPEC)
2,276,967

12
 Mexico
2,186,877

13
 Nigeria (OPEC)
1,999,885

14
 Angola (OPEC)
1,769,615

15
 Norway
1,647,975

16
 Kazakhstan
1,595,199

17
 Qatar (OPEC)
1,522,902

18
 Algeria (OPEC)
1,348,361

19
 Oman
1,006,841

20
 United Kingdom
939,760

21
 Colombia
897,784

22
 Indonesia
833,667

23
 Azerbaijan
833,538

24
 India
734,180

25
 Malaysia
661,240

26
 Ecuador (OPEC)
548,421

27
 Argentina
510,560

28
 Egypt
494,325

29
 Libya (OPEC)
384,686

30
 Congo, Republic of the
308,363

31
 Vietnam
301,850

32
 Australia
289,749

33
 Thailand
257,525

34
 Sudan and  South Sudan
255,000

35
 Turkmenistan
230,779

36
 Equatorial Guinea (OPEC)
227,000

37
 Gabon (OPEC)
210,820

38
 Denmark
140,637

39
 Chad
110,156

40
 Brunei
109,117

41
 Ghana
100,549

42
 Cameroon
93,205

43
 Pakistan
84,746

44
 Romania
77,910

45
 Italy
70,675

46
 Timor-Leste
60,661

47
 Trinidad and Tobago
60,090

48
 Bolivia
58,077

49
 Papua New Guinea
56,667

50
 Uzbekistan
52,913

51.5
 Bahrain
50,000

51.5
 Cuba
50,000

53
 Turkey
49,497

54
 Tunisia
48,757

55
 Germany
46,839

56
 Peru
40,266

57
 New Zealand
35,574

58
 Ukraine
31,989

59.5
 Ivory Coast
30,000

59.5
 Syria
30,000

61
 Belarus
25,000

62
 Mongolia
23,426

63
 Albania
22,915

64
 Yemen
22,000

65
 Poland
20,104

67
 Congo, Democratic Republic of the
20,000

67
 Philippines
20,000

67
 Serbia
20,000

69
 Netherlands
18,087

70
 Suriname
17,000

71
 France
16,418

72
 Austria
15,161

73
 Myanmar
15,000

74
 Hungary
13,833

75
 Croatia
13,582

76
 Niger
13,000

77
 Guatemala
8,977

78
 Mauritania
5,000

79
 Chile
4,423

80
 Bangladesh
4,189

81
 Japan
3,918

82
 Greece
3,172

83
 Spain
2,667

84
 Czech Republic
2,333

86
 Belize
2,000

86
 Lithuania
2,000

86
 South Africa
2,000

89
 Barbados
1,000

89
 Bulgaria
1,000

89
 Kyrgyzstan
1,000

91
 Georgia
400

92
 Israel
390

93
 Slovakia
200

94
 Taiwan
196

95
 Tajikistan
180

96
 Morocco
160

97
 Jordan
22

98
 Slovenia
5