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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
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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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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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Scientists discover stardust in Antarctic snow
on August 20, 2019 at 4:04 pm
A team of scientists hauled 500 kilograms of fresh snow back from Antarctica, melted it, and sifted through the particles that remained. Their analysis yielded a surprise: The snow held significant amounts of a form of iron that isn't naturally produced on Earth.
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Assessing the possible safety issues in the...
on August 20, 2019 at 1:50 pm
A team of researchers with the Chinese Academy of Sciences has carried out an assessment of possible safety issues tied to the rise of the second nuclear era. In their paper published in Proceedings of the National Academy of Sciences, the group describes the factors that led to the rise of a second nuclear era and possible safety concerns that need to be addressed.
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Physicists design an experiment to pin down the...
on August 20, 2019 at 12:01 pm
Nearly all of the oxygen in our universe is forged in the bellies of massive stars like our sun. As these stars contract and burn, they set off thermonuclear reactions within their cores, where nuclei of carbon and helium can collide and fuse in a rare though essential nuclear reaction that generates much of the oxygen in the universe.
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Lithium fluoride crystals 'see' heavy ions with...
on August 19, 2019 at 4:37 pm
Lithium fluoride crystals have recently been used to register the tracks of nuclear particles. Physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow have just demonstrated that these crystals are also ideal for detecting tracks of high-energy ions of elements even as heavy as iron.
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New model agrees with old: Nuclear war between US...
on August 19, 2019 at 1:29 pm
A team of researchers with Rutgers University, the National Center for Atmospheric Research and the University of Colorado has found that a new climate model agrees with an older climate model—a nuclear war between the U.S and Russia would result in a nuclear winter. They have published their findings in the Journal of Geophysical Research: Atmospheres.