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CODATA Internationally recommended values of the Fundamental Physical Constants, Atomic and Nuclear (NIST Reference on Constants, Units and Uncertainty)
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atom : the smallest particle of an element that can exist either alone or in combination — Webster
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Atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale).
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom’s mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion.
The electrons of an atom are attracted to the protons in an atomic nucleus by this electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by a different force, the nuclear force, which is usually stronger than the electromagnetic force repelling the positively charged protons from one another. Under certain circumstances, the repelling electromagnetic force becomes stronger than the nuclear force, and nucleons can be ejected from the nucleus, leaving behind a different element: nuclear decay resulting in nuclear transmutation.
The number of protons in the nucleus defines to what chemical element the atom belongs: for example, all copper atoms contain 29 protons. The number of neutrons defines the isotope of the element. The number of electrons influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature and is the subject of the discipline of chemistry. — Wikipedia
Atoms (Eric Weisstein’s World of Physics, Wolfram Research)
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Science
Atomic Physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change.
The term atomic physics can be associated with nuclear power and nuclear weapons, due to the synonymous use of atomic and nuclear in standard English. Physicists distinguish between atomic physics — which deals with the atom as a system consisting of a nucleus and electrons — and nuclear physics, which considers atomic nuclei alone. — Wikipedia
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons. — Wikipedia
Preservation
History
How Can You See an Atom? – Legends of Chemistry (American Chemical Society)
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National Museum of Nuclear Science & History (Albuquerque, New Mexico)
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WorldCat, Library of Congress, UPenn Online Books, Open Library
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https://fusedweb.llnl.gov/
Atoms Around Us (Chem4Kids)
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Atom in a Box: Real-Time Visualization of the Quantum Mechanical Atomic Orbitals (Dauger Research)
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Scientist Splits Atom, Finds Toy Prize Inside (Satire Wire)
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The Man Who Hunts Hidden Radioactive Objects (Chris Baraniuk, BBC Future)
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OEDILF: The Omnificent English Dictionary In Limerick Form
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Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
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Plants use a single communication route when...
on November 18, 2019 at 12:24 pm
Researchers in Japan and the U.K. have discovered new details of how young leaves build their first chloroplasts, the energy factories of plant cells. The researchers identified a new role for a protein that was first identified 25 years ago, but which had defied characterization until now.
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He saw a Marshall Islands nuclear bomb test up...
on November 15, 2019 at 3:00 pm
In the summer of 1952, Alan Jones, an industrious redhead with an impish smile, yearned for excitement and adventure. He drove down the California coast from Berkeley to La Jolla, hoping to join an oceanographic expedition heading to the South Pacific.
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Carbon dots make calcium easier to track
on November 12, 2019 at 4:20 pm
In hospitals, doctors often advise patients to take calcium supplements. But does the calcium get into the cells that need it? Until recently, it's been hard to tell.
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The alchemy of merging neutron stars
on November 7, 2019 at 3:26 pm
For the first time, astronomers have identified a chemical element that was freshly formed by the merging of two neutron stars. The underlying mechanism, called the r-process—also known as rapid neutron capture—is considered to be the origin of large quantities of elements heavier than iron.
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New measurement yields smaller proton radius
on November 6, 2019 at 6:00 pm
Using the first new method in half a century for measuring the size of the proton via electron scattering, the PRad collaboration has produced a new value for the proton's radius in an experiment conducted at the Department of Energy's Thomas Jefferson National Accelerator Facility.