| Helium atom | | | | An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) is in reality spherically symmetric, although for more complicated nuclei this is not always the case. The black bar is one ångström, equal to 10−10 m or 100,000 fm. | | Classification | | | | Properties | | | An atom is the smallest particle that comprises a chemical element. An atom consists of an electron cloud that surrounds a dense nucleus. This nucleus contains positively charged protons and electrically neutral neutrons, whereas the surrounding cloud is made up of negatively charged electrons. When the number of protons in the nucleus equals the number of electrons, the atom is electrically neutral; otherwise it is an ion and has a net positive or negative charge. An atom is classified according to its number of protons and neutrons: the number of protons determines the chemical element and the number of neutrons determines the isotope of that element. The concept of the atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and the early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was not indivisible. The principles of quantum mechanics, including the wave–particle duality of matter, were used to successfully model the atom.[1][2] Wiktionary has related dictionary definitions, such as: atom Atom refers to smallest possible particle of ordinary matter. ...
Image File history File links This is a lossless scalable vector image. ...
General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ...
The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...
Electron cloud is a term used- if not originally coined- by the nobelaurate and acclaimed educator Richard Feynman in The Feynman Lectures on Physics, for discussing exactly what is an electron?. This intuitive model provides a simplified way of visualizing an electron as a solution of the Schrödinger equation. ...
An ångström or aangstroem (the official transliteration), or angstrom (symbol Å) is a non-SI unit of length that is internationally recognized, equal to 0. ...
This article is about the unit of length. ...
Femtometre (American spelling: femtometer) is an SI measure of length that is equal to 10−15 (femto) of a metre. ...
The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ...
Stylized lithium-7 atom: 3 protons, 4 neutrons & 3 electrons (~1800 times smaller than protons/neutrons). ...
For other uses of G, see G (disambiguation). ...
This box: Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...
This article is about the electrically charged particle. ...
DIAMETER is a computer networking protocol for AAA (Authentication, Authorization and Accounting). ...
One picometre is defined as 1x10-12 metres, in standard units. ...
General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ...
General Name, Symbol, Number caesium, Cs, 55 Chemical series alkali metals Group, Period, Block 1, 6, s Appearance silvery gold Standard atomic weight 132. ...
// Atomic radii Notes The radius of an atom is not a uniquely defined property and depends on the definition. ...
Helium atom (schematic) Showing two protons (red), two neutrons (green) and two electrons (yellow). ...
For other uses, see Electron (disambiguation). ...
The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...
For other uses, see Proton (disambiguation). ...
This article or section does not adequately cite its references or sources. ...
The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ...
Electron cloud is a term used- if not originally coined- by the nobelaurate and acclaimed educator Richard Feynman in The Feynman Lectures on Physics, for discussing exactly what is an electron?. This intuitive model provides a simplified way of visualizing an electron as a solution of the Schrödinger equation. ...
The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...
This box: Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...
For other uses, see Proton (disambiguation). ...
This article or section does not adequately cite its references or sources. ...
For other uses, see Electron (disambiguation). ...
This article is about the electrically charged particle. ...
The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ...
For other uses, see Isotope (disambiguation). ...
A chemist pours from a round-bottom flask. ...
Not to be confused with physician, a person who practices medicine. ...
For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ...
This box: In physics and chemistry, wave–particle duality is the concept that all matter exhibits both wave-like and particle-like properties. ...
Scientific modelling is the process of generating abstract or conceptual models. ...
Relative to everyday experience, atoms are minuscule objects with proportionately tiny masses that can only be observed individually using special instruments such as the scanning tunneling microscope. More than 99.9% of an atom's mass is concentrated in the nucleus,[3] with protons and neutrons having about equal mass. In atoms with too many or too few neutrons relative to the number of protons, the nucleus is unstable and subject to radioactive decay.[4] The electrons surrounding the nucleus occupy a set of stable energy levels, or orbitals, and they can transition between these states by the absorption or emission of photons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties. Image of reconstruction on a clean Au(100) surface. ...
Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ...
A quantum mechanical system can only be in certain states, so that only certain energy levels are possible. ...
In chemistry, an atomic orbital is the region in which an electron may be found around a single atom. ...
In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ...
For other senses of this word, see magnetism (disambiguation). ...
History -
Main articles: Atomic theory and Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny quantities has been around for millennia, but these ideas were founded in abstract, philosophical reasoning rather than experimentation and empirical observation. The nature of atoms in philosophy varied considerably over time and between cultures and schools, and often had spiritual elements. Nevertheless, the basic idea of the atom was adopted by scientists thousands of years later because it elegantly explained new discoveries in the field of chemistry.[5] This article focuses on the historical models of the atom. ...
Concern has been expressed that this article or section is missing information about: discussions of existence of atoms among prominent physicists up to the end of 19th century. ...
The earliest references to the concept of atoms date back to ancient India in the 6th century BCE.[6] The Nyaya and Vaisheshika schools developed elaborate theories of how atoms combined into more complex objects (first in pairs, then trios of pairs).[7] The references to atoms in the West emerged a century later from Leucippus whose student, Democritus, systemized his views. In approximately 450 BCE, Democritus coined the term átomos (Greek ἄτομος), which means "uncuttable" or "the smallest indivisible particle of matter", i.e., something that cannot be divided. Although the Indian and Greek concepts of the atom were based purely on philosophy, modern science has retained the name coined by Democritus.[5] The History of India begins with the Indus Valley Civilization, which flourished in the north-western part of the Indian subcontinent from 3300 to 1700 BCE. This Bronze Age civilization was followed by the Iron Age Vedic period, which witnessed the rise of major kingdoms known as the Mahajanapadas. ...
BCE is a TLA that may stand for: Before the Common Era, date notation equivalent to BC (e. ...
(Sanskrit ni-Äyá, literally recursion, used in the sense of syllogism, inference)) is the name given to one of the six orthodox or astika schools of Hindu philosophy—specifically the school of logic. ...
Vaisheshika, also Vaisesika, (Sanskrit: वैशॆषिक)is one of the six Hindu schools of philosophy (orthodox Vedic systems) of India. ...
Vaisheshika, also Vaisesika, (Sanskrit: वैशॆषिक)is one of the six Hindu schools of philosophy (orthodox Vedic systems) of India. ...
This article is about the philosopher. ...
‎ Democritus (Greek: ) was a pre-Socratic Greek materialist philosopher (born at Abdera in Thrace ca. ...
Further progress in the understanding of atoms did not occur until the science of chemistry began to develop. In 1661, the natural philosopher Robert Boyle published The Sceptical Chymist in which he argued that matter was composed of various combinations of different "corpuscules" or atoms, rather than the classical elements of air, earth, fire and water.[8] In 1789 the term element was defined by the French nobleman and scientific researcher Antoine Lavoisier to mean basic substances that could not be further broken down by the methods of chemistry.[9] For other uses, see Chemistry (disambiguation). ...
Natural philosophy or the philosophy of nature, known in Latin as philosophia naturalis, is a term applied to the objective study of nature and the physical universe that was regnant before the development of modern science. ...
For the American art director and production designer, see Robert F. Boyle Robert Boyle (25 January 1627 – 30 December 1691) was a natural philosopher, chemist, physicist, inventor, and early gentleman scientist, noted for his work in physics and chemistry. ...
This article or section does not adequately cite its references or sources. ...
Many ancient philosophies used a set of archetypal classical elements to explain patterns in nature. ...
Lavoisier redirects here. ...
 Various atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy (1808) In 1803, the Englishman John Dalton, an instructor and natural philosopher, used the concept of atoms to explain why elements always reacted in a ratio of small whole numbers—the law of multiple proportions—and why certain gases dissolved better in water than others. He proposed that each element consists of atoms of a single, unique type, and that these atoms could join to each other, to form chemical compounds.[10][11] Image File history File links A_New_System_of_Chemical_Philosophy_fp. ...
Image File history File links A_New_System_of_Chemical_Philosophy_fp. ...
John Dalton John Dalton (September 6, 1766 – July 27, 1844) was an English chemist and physicist, born at Eaglesfield, near Cockermouth in Cumberland. ...
John Dalton John Dalton (September 6, 1766 – July 27, 1844) was an English chemist and physicist, born at Eaglesfield, near Cockermouth in Cumberland. ...
In mathematics, a natural number can mean either an element of the set {1, 2, 3, ...} (i. ...
In chemistry, the law of multiple proportions is one of the most basic laws of stoichiometry. ...
Additional validation of particle theory (and by extension atomic theory) occurred in 1827 when 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". J. Desaulx suggested in 1877 that the phenomenon was caused by the thermal motion of water molecules, and in 1905 Albert Einstein produced the first mathematical analysis of the motion, thus confirming the hypothesis.[12][13] This article focuses on the historical models of the atom. ...
Pinguicula grandiflora commonly known as a Butterwort Example of a cross section of a stem [1] Botany is the scientific study of plant life. ...
Robert Brown (1773–1858) Robert Brown (December 21, 1773–June 10, 1858) is acknowledged as the leading British botanist to collect in Australia during the first half of the 19th century. ...
A microscope (Greek: (micron) = small + (skopein) = to look at) is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. ...
Three different views of Brownian motion, with 32 steps, 256 steps, and 2048 steps denoted by progressively lighter colors. ...
“Einstein†redirects here. ...
The physicist J. J. Thomson, through his work on cathode rays in 1897, discovered the electron and its subatomic nature, which destroyed the concept of atoms as being indivisible units.[14] Thomson believed that the electrons were distributed throughout the atom, with their charge balanced by the presence of a uniform sea of positive charge (the plum pudding model). Sir Joseph John “J.J.†Thomson, OM, FRS (18 December 1856 – 30 August 1940) was a British physicist and Nobel laureate, credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer. ...
A schematic diagram of a Crookes tube apparatus. ...
A schematic representation of the plum pudding model of the atom. ...
 A Bohr model of the hydrogen atom, showing an electron jumping between fixed orbits and emitting a photon of energy with a specific frequency However, in 1909, researchers under the direction of physicist Ernest Rutherford bombarded a sheet of gold foil with helium ions and discovered that a small percentage were deflected through much larger angles than was predicted using Thomson's proposal. Rutherford interpreted the gold foil experiment as suggesting that the positive charge of an atom and most of its mass was concentrated in a nucleus at the center of the atom (the Rutherford model), with the electrons orbiting it like planets around a sun. Positively charged helium ions passing close to this dense nucleus would then be deflected away at much sharper angles.[15] Image File history File links Bohr_model. ...
Image File history File links Bohr_model. ...
In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ...
Ernest Rutherford, 1st Baron Rutherford of Nelson OM PC FRS (30 August 1871 – 19 October 1937), widely referred to as Lord Rutherford, was a chemist (B.Sc. ...
Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed. ...
A stylised representation of the Rutherford model of a lithium atom (nuclear structure anachronistic) The Rutherford model or planetary model was a model of the atom devised by Ernest Rutherford. ...
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.[16] 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.[17] Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ...
Radiochemistry deals with the use of radioactivity to study ordinary chemical reactions. ...
Frederick Soddy in 1922. ...
For other uses, see Isotope (disambiguation). ...
It has been suggested that this article or section be merged into Isotope. ...
Meanwhile, in 1913, physicist Niels Bohr revised Rutherford's model by suggesting that the electrons were confined into clearly defined orbits, and could jump between these, but could not freely spiral inward or outward in intermediate states.[18] An electron must absorb or emit specific amounts of energy to transition between these fixed orbits. When the light from a heated material is passed through a prism, it produced a multi-colored spectrum. The appearance of fixed lines in this spectrum was successfully explained by the orbital transitions.[19] Niels Henrik David Bohr (October 7, 1885 – November 18, 1962) was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. ...
For other uses, see Light (disambiguation). ...
If a shaft of light entering a prism is sufficiently narrow, a spectrum results. ...
This article deals with the general meaning of spectrum and the history of its use. ...
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ...
In 1926, Erwin Schrödinger, using Louis de Broglie's 1924 proposal that particles behave to an extent like waves, developed a mathematical model of the atom that described the electrons as three-dimensional waveforms, rather than point particles. A consequence of using waveforms to describe electrons is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at the same time; this became known as the uncertainty principle. In this concept, for each measurement of a position one could only obtain a range of probable values for momentum, and vice versa. Although this model was difficult to visually conceptualize, it 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 orbital zones around the nucleus where a given electron is most likely to exist.[20][21] Schrödinger in 1933, when he was awarded the Nobel Prize in Physics Bust of Schrödinger, in the courtyard arcade of the main building, University of Vienna, Austria. ...
Louis-Victor-Pierre-Raymond, 7th duc de Broglie, generally known as Louis de Broglie (August 15, 1892–March 19, 1987), was a French physicist and Nobel Prize laureate. ...
Waveform quite literally means the shape and form of a signal, such as a wave moving across the surface of water, or the vibration of a plucked string. ...
A spatial point is an entity with a location in space but no extent (volume, area or length). ...
This article is about momentum in physics. ...
In quantum physics, the outcome of even an ideal measurement of a system is not deterministic, but instead is characterized by a probability distribution, and the larger the associated standard deviation is, the more uncertain we might say that that characteristic is for the system. ...
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ...
 Schematic diagram of a simple mass spectrometer The development of the mass spectrometer allowed the exact mass of atoms to be measured. 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 demonstrate that isotopes had different masses. The mass of these isotopes varied by integer amounts, called the whole number rule.[22] The explanation for these different atomic isotopes awaited the discovery of the neutron, a neutral-charged 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.[23] Image File history File links No higher resolution available. ...
Image File history File links No higher resolution available. ...
Mass spectrometry (previously called mass spectroscopy (deprecated) or informally, mass-spec and MS) is an analytical technique that measures the mass-to-charge ratio of ions. ...
Francis William Aston (born Harborne, Birmingham, September 1, 1877; died Cambridge, November 20, 1945) was a British chemist and physicist who won the 1922 Nobel Prize in Chemistry for his discovery, by means of his mass spectrograph, of isotopes, in a large number of non-radioactive elements, and for his...
The Whole Number Rule states that the masses of the elements are whole number multiples of the mass of the hydrogen atom. ...
This article or section does not adequately cite its references or sources. ...
For other uses, see Proton (disambiguation). ...
Sir James Chadwick, CH (20 October 1891 – 24 July 1974) was an English physicist and Nobel laureate who is best known for discovering the neutron. ...
In the 1950s, the development of improved particle accelerator and particle detectors allowed scientists to study the impacts of atoms moving at high energies.[24] Neutrons and protons were found to be hadrons, or composites of smaller particles called quarks. Standard models of nuclear physics were developed that successfully explained the properties of the nucleus in terms of these sub-atomic particles and the forces that govern their interactions.[25] Atom Smasher redirects here. ...
The Compact Muon Solenoid (CMS) is an example of a large particle detector. ...
A hadron, in particle physics, is a subatomic particle which experiences the nuclear force. ...
For other uses, see Quark (disambiguation). ...
Around 1985, Steven Chu and co-workers at Bell Labs developed a technique for lowering the temperatures of atoms using lasers. In the same year, a team led by William D. Phillips managed to contain atoms of sodium in a magnetic trap. The combination of these two techniques and a method based on the Doppler effect, developed by Claude Cohen-Tannoudji and his group, allows small numbers of atoms to be cooled to several microkelvin. This allows the atoms to be studied with great precision, and later led to the discovery of Bose-Einstein condensation.[26] Steven Chu (Chinese: ; pinyin: ), born 1948 in St. ...
Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ...
For other uses, see Laser (disambiguation). ...
Photograph of William Daniel Phillips William Daniel Phillips (born November 5, 1948 in Wilkes-Barre, Pennsylvania) is an American physicist. ...
A magnetic trap uses a magnetic gradient in order to trap neutral particles with a magnetic moment. ...
A source of waves moving to the left. ...
Claude Cohen-Tannoudji (born April 1, 1933) is a French physicist working at the École Normale Supérieure in Paris, France, where he has also studied physics. ...
For other uses, see Kelvin (disambiguation). ...
A Bose–Einstein condensate is a phase of matter formed by bosons cooled to temperatures very near to absolute zero. ...
Historically, single atoms have been prohibitively small for scientific applications. Recently, devices have been constructed that use a single metal atom connected through organic ligands to construct a single electron transistor.[27] Experiments have been carried out by trapping and slowing single atoms using laser cooling in a cavity to gain a better physical understanding of matter.[28] In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a...
In physics, a Coulomb blockade, named after Charles-Augustin de Coulomb, is the increased resistance at small bias voltages of an electronic device comprising at least one low-capacitance tunnel junction. ...
Laser cooling is a technique that uses light to cool atoms to a very low temperature. ...
Components
Subatomic particles -
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 consist of the electron, the proton and, for atoms other than hydrogen-1, the neutron. Helium atom (schematic) Showing two protons (red), two neutrons (green) and two electrons (yellow). ...
Helium atom (schematic) Showing two protons (red), two neutrons (green) and two electrons (yellow). ...
For other uses, see Electron (disambiguation). ...
For other uses, see Proton (disambiguation). ...
This article is about the chemistry of hydrogen. ...
This article or section does not adequately cite its references or sources. ...
The electron is by far the least massive of these particles at 9.11×10−28 g, with a negative electrical charge and a size that is too small to be measured using available techniques.[29] Protons have a positive charge and a mass 1,836 times that of the electron, at 1.6726×10−24 g, although this can be reduced by changes to the atomic binding energy. Neutrons have no electrical charge and have a free mass of 1,839 times the mass of electrons,[30] or 1.6929×10−24 g. Neutrons and protons have comparable dimensions—on the order of 2.5×10−15 m—although the 'surface' of these particles is not sharply defined.[31] This box: Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...
Binding energy is the energy required to disassemble a whole into separate parts. ...
This article is about the unit of length. ...
In the Standard Model of physics, both protons and neutrons are composed of elementary particles called quarks. The quark is a type of fermion, one of the two basic constituents of matter—the other being the lepton, of which the electron is an example. There are six types of quarks, and each has a fractional electric charge of either +2/3 or −1/3. Protons are composed of two up quarks and one down quark, while a neutron consists of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two particles. The quarks are held together by the strong nuclear force, which is mediated by gluons. The gluon is a member of the family of bosons, which are elementary particles that mediate physical forces.[32][33] The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ...
For the novel, see The Elementary Particles. ...
For other uses, see Quark (disambiguation). ...
In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ...
For the former Greek currency unit, see Greek drachma. ...
The up quark is a first-generation quark with a charge of +(2/3)e. ...
The down quark is a first-generation quark with a charge of -(1/3)e. ...
The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ...
In particle physics, gluons are subatomic particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei. ...
In particle physics, bosons are particles with an integer spin, as opposed to fermions which have half-integer spin. ...
For other uses, see Force (disambiguation). ...
Nucleus -
Main article: Atomic nucleus All of 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 ![begin{smallmatrix}1.07 cdot sqrt[3]{A}end{smallmatrix}](http://upload.wikimedia.org/math/4/8/f/48f98c98c376d8dadf6893065ae83c45.png) fm, where A is the total number of nucleons.[34] 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.[35] The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...
The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...
In physics a nucleon is a collective name for two baryons: the neutron and the proton. ...
This article is about the force sometimes called the strong nuclear force. For the weak nuclear force or weak interaction, see that article. ...
Femtometre (American spelling: femtometer) is an SI measure of length that is equal to 10−15 (femto) of a metre. ...
In physics, the electrostatic force is the force arising between static (that is, non-moving) electric charges. ...
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 number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay.[36] The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ...
See also: List of elements by atomic number In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. ...
For other uses, see Isotope (disambiguation). ...
Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ...
The neutron and the proton are different types of fermions. The Pauli exclusion principle is a quantum mechanical effect that prohibits identical fermions (such as multiple protons) from occupying the same quantum physical state at the same time. Thus every proton in the nucleus must occupy a different state, with its own energy level, and the same rule applies to all of the neutrons. (This prohibition does not apply to a proton and neutron occupying the same quantum state.)[37] In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ...
The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925. ...
For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ...
A nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactive decay that causes the number of protons and neutrons to more closely match. As a result, atoms with matching numbers of protons and neutrons are more stable against decay. However, with increasing atomic number, the mutual repulsion of the protons requires an increasing proportion of neutrons to maintain the stability of the nucleus, which slightly modifies this trend of equal numbers of protons to neutrons.[37]
 This diagram illustrates a nuclear fusion process that forms a deuterium nucleus, consisting of a proton and a neutron, from two protons. A positron (e +)—an antimatter electron—is emitted along with an electron neutrino. 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. 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.[38] 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. In such processes that change the number of protons in a nucleus, the atom becomes an atom of a different chemical element.[39][40] Image File history File links Wpdms_physics_proton_proton_chain_1. ...
Image File history File links Wpdms_physics_proton_proton_chain_1. ...
The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ...
For other senses of this term, see antimatter (disambiguation). ...
For other uses, see Neutrino (disambiguation). ...
The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ...
The Coulomb barrier, named after physicist Charles-Augustin de Coulomb (1736—1806), is the energy barrier due to electrostatic interaction that two nuclei need to overcome so they can get close enough to undergo nuclear fusion. ...
For the generation of electrical power by fission, see Nuclear power plant. ...
The mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate particles. The difference between these two values is emitted as energy, 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 the binding energy of the nucleus.[41] “Einstein†redirects here. ...
5-meter-tall sculpture of Einsteins 1905 E = mc2 formula at the 2006 Walk of Ideas, Germany In physics, mass–energy equivalence is the concept that any mass has an associated energy and vice versa. ...
A line showing the speed of light on a scale model of Earth and the Moon, taking about 1â…“ seconds to traverse that distance. ...
Binding energy is the energy required to disassemble a whole into separate parts. ...
The fusion of two nuclei that have lower atomic numbers than iron and nickel is an exothermic process that releases more energy than is required to bring them together.[42] It is this energy-releasing process that makes nuclear fusion in stars a self-sustaining reaction. For heavier nuclei, the total binding energy begins to decrease. That means fusion processes with nuclei that have higher atomic numbers 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.[37] General Name, symbol, number iron, Fe, 26 Chemical series transition metals Group, period, block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ...
For other uses, see Nickel (disambiguation). ...
In chemistry, an exothermic reaction is one that releases heat. ...
This article is about the astronomical object. ...
In Chemistry an endothermic reaction is one in which the reactants have less energy than the products, and thus a net input of energy, usually in the form of heat, is required. ...
Hydrostatic equilibrium occurs when compression due to gravity is balanced by a pressure gradient which creates a pressure gradient force in the opposite direction. ...
Electron cloud -
Main article: Electron cloud  This is an example of a potential well, showing the minimum energy V( x) needed to reach each position x. A particle with energy E is constrained to a range of positions between x1 and x2. 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 in order 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 the exterior. Electron cloud is a term used- if not originally coined- by the nobelaurate and acclaimed educator Richard Feynman in The Feynman Lectures on Physics, for discussing exactly what is an electron?. This intuitive model provides a simplified way of visualizing an electron as a solution of the Schrödinger equation. ...
In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. ...
Electrostatics is the branch of physics that deals with the force exerted by a static (i. ...
A potential well is the region surrounding a local minimum of potential energy. ...
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 will appear to be at a particular location when its position is measured. Only a discrete (or quantized) set of these orbitals exist around the nucleus, as other possible wave patterns will rapidly decay into a more stable form.[43] Orbitals can have one or more ring or node structures, and they differ from each other in size, shape and orientation.[44] This box: In physics and chemistry, wave–particle duality is the concept that all matter exhibits both wave-like and particle-like properties. ...
Vibration and standing waves in a string, The fundamental and the first 6 overtones A standing wave, also known as a stationary wave, is a wave that remains in a constant position. ...
In chemistry, an atomic orbital is the region in which an electron may be found around a single atom. ...
 This illustration shows the wave functions of the first five atomic orbitals. Note how each of the three 2p orbitals display a single angular node that has an orientation and a minimum at the center. 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.[43] A standing wave. ...
A quantum mechanical system can only be in certain states, so that only certain energy levels are possible. ...
In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ...
Spontaneous emission is the process by which a molecule in an excited state drops to the ground state, resulting in the creation of a photon. ...
In physics, atomic spectral lines are of two types: An emission line is formed when an electron makes a transition from a particular discrete energy level of an atom, to a lower energy state, emitting a photon of a particular energy and wavelength. ...
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.[45] 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.[46] Electron binding energy (BE) is the energy required to release an electron from its atomic or molecular orbital. ...
Binding energy is the energy required to disassemble a whole into separate parts. ...
In quantum mechanics, a stationary state is an eigenstate of a Hamiltonian, or in other words, a state of definite energy. ...
This box: Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...
This article is about the electrically charged particle. ...
A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ...
3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ...
Look up chemical compound in Wiktionary, the free dictionary. ...
An ionic crystal is a crystal consisting of ions bound together by their electrostatic attraction. ...
Covalent redirects here. ...
Frost crystallization on a shrub. ...
Properties By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with the same number of protons but a different number of neutrons are different isotopes of the same element. Hydrogen atoms, for example, always have only a single proton, but isotopes exist with no neutrons (hydrogen-1, sometimes called protium, by far the most common form), one neutron (deuterium) and two neutrons (tritium).[47] The known elements form a continuous range of atomic numbers from hydrogen with a single proton up to the 118-proton element ununoctium.[48] All known isotopes of elements with atomic numbers greater than 82 are radioactive.[49][50] The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ...
For other uses, see Isotope (disambiguation). ...
Depiction of a hydrogen atom showing the diameter as about twice the Bohr model radius. ...
Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ...
Tritium (symbol T or ³H) is a radioactive isotope of hydrogen. ...
General Name, Symbol, Number ununoctium, Uuo, 118 Chemical series noble gases Group, Period, Block 18, 7, p Appearance unknown, probably colorless Atomic mass predicted, (314) g/mol Electron configuration perhaps [Rn] 5f14 6d10 7s2 7p6 (guess based on radon) Electrons per shell 2, 8, 18, 32, 32, 18, 8 Phase...
Mass -
Main article: Atomic mass Because the large majority of an atom's mass comes from the protons and neutrons, the total number of these particles in an atom is called the mass number. The mass of an atom at rest is often expressed using the unified atomic mass unit (u), which is also called a Dalton (Da). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately 1.66×10−24 g.[51] hydrogen-1, the lightest isotope of hydrogen and the atom with the lowest mass, has an atomic weight of 1.007825 u.[52] An atom has a mass approximately equal to the mass number times the atomic mass unit.[53] The heaviest stable atom is lead-208,[49] with a mass of 207.9766521 u.[54] Stylized lithium-7 atom: 3 protons, 4 neutrons & 3 electrons (~1800 times smaller than protons/neutrons). ...
The mass number (A), also called atomic mass number (not to be confused with atomic number (Z) which denotes the number of protons in a nucleus) or nucleon number, is the number of nucleons (protons and neutrons) in an atomic nucleus. ...
The invariant mass or intrinsic mass or proper mass or just mass is a measurement or calculation of the mass of an object that is the same for all frames of reference. ...
The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic and molecular masses. ...
Carbon 12 is a stable isotope of the element carbon. ...
Depiction of a hydrogen atom showing the diameter as about twice the Bohr model radius. ...
As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles. The mole is defined such that one mole of any element will always have the same number of atoms (about 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 will have a mass of 1 g. Carbon, for example, has an atomic mass of 12 u, so a mole of carbon atoms weighs 12 g.[51] The mole (symbol: mol) is the SI base unit that measures an amount of substance. ...
The Avogadro constant (symbols: L, NA), also called the Avogadro number and, in German scientific literature, sometimes also known as the Loschmidt constant/number, is formally defined to be the number of entities in one mole,[1][2] that is the number of carbon-12 atoms in 12 grams (0. ...
For other uses, see Carbon (disambiguation). ...
Size -
Main article: Atomic radius Atoms lack a well-defined outer boundary, so the dimensions are usually described in terms of 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.[55] 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).[56] Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm.[57] These dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they can not be viewed using an optical microscope. However, individual atoms can be observed using a scanning tunneling microscope. Atomic radius: Ionic radius Covalent radius Metallic radius van der Waals radius edit Atomic radius, and more generally the size of an atom, is not a precisely defined physical quantity, nor is it constant in all circumstances. ...
A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ...
In chemistry coordination number (c. ...
For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ...
In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ...
The Periodic Table redirects here. ...
One picometre is defined as 1x10-12 metres, in standard units. ...
General Name, Symbol, Number caesium, Cs, 55 Chemical series alkali metals Group, Period, Block 1, 6, s Appearance silvery gold Standard atomic weight 132. ...
For other uses, see Light (disambiguation). ...
A nanometre (American spelling: nanometer, symbol nm) (Greek: νάνος, nanos, dwarf; μετÏÏŽ, metrÏŒ, count) is a unit of length in the metric system, equal to one billionth of a metre (or one millionth of a millimetre), which is the current SI base unit of length. ...
An 1879 Carl Zeiss Jena Optical microscope. ...
Image of reconstruction on a clean Au(100) surface. ...
Some examples will demonstrate the minuteness of the atom. A typical human hair is about 1 million carbon atoms in width.[58] A single drop of water contains about 2 sextillion (2×1021) atoms of oxygen, and twice the number of hydrogen atoms.[59] A single carat diamond with a mass of 0.2 g contains about 10 sextillion atoms of carbon.[60] If an apple was magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple.[61] Main article: Names of large numbers A sextillion is a number written as either: a 1 followed by 21 zeros (10 to the 21st power, as used in the short scale system of numeration. ...
The carat is a unit of mass used for measuring gems and pearls, and is exactly 200 milligrams. ...
This article is about the mineral. ...
Main article: Names of large numbers A sextillion is a number written as either: a 1 followed by 21 zeros (10 to the 21st power, as used in the short scale system of numeration. ...
For other uses, see Carbon (disambiguation). ...
Radioactive decay -
 This diagram shows the half-life (T ½) in seconds of various isotopes with Z protons and N neutrons. 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. |
