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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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Encyclopedia
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
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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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https://fusedweb.llnl.gov/
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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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Physicists get thousands of semiconductor nuclei...
on February 21, 2019 at 7:00 pm
A team of Cambridge researchers have found a way to control the sea of nuclei in semiconductor quantum dots so they can operate as a quantum memory device. […]
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Correlated nucleons may solve 35-year-old mystery
on February 20, 2019 at 6:00 pm
A careful re-analysis of data taken at the Department of Energy's Thomas Jefferson National Accelerator Facility has revealed a possible link between correlated protons and neutrons in the nucleus and a 35-year-old mystery. The data have led to the extraction of a universal function that describes the EMC Effect, the once-shocking discovery that quarks inside nuclei have lower average momenta than predicted, and supports an explanation for the effect. The study has been published in the journal […]
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Mechanism of iron-based hydrogen bond cleavage...
on February 19, 2019 at 1:00 pm
Hydrogen-based fuel cells hold promise for sustainable power generation, but to become practical they need to be more efficient and cost effective. Scientists at Pacific Northwest National Laboratory's (PNNL's) Center for Molecular Electrocatalysis (CME) are working to understand the fundamental reactivity of H2 that could contribute to making hydrogen a more widely used fuel source. Working with a rare iron-based paramagnetic complex, a CME-based research team for the first time reported […]
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For scientists, the ripple effects of the...
on February 18, 2019 at 3:53 pm
Matt Helgeson knew it was time to pull the plug. For weeks, the University of California, Santa Barbara professor of chemical engineering had held out hope that politicians in Washington would find a way to end the government shutdown. If they did, his graduate students could still make their long-planned trip to Maryland to conduct experiments at the National Institute of Standards and Technology's Center for Neutron Research in mid-January. […]
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World's finest gold specimen probed with Los...
on February 18, 2019 at 1:02 pm
Using neutron characterization techniques a team of scientists have peered inside one of the most unique examples of wire gold, understanding for the first time the specimen's structure and possible formation process. The 263 gram, 12 centimeter tall specimen, known as the Ram's Horn, belongs to the collection of the Mineralogical and Geological Museum Harvard University (MGMH). […]