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CODATA Internationally recommended values of the Fundamental Physical Constants, Atomic and Nuclear (NIST Reference on Constants, Units and Uncertainty)
Radiation, Radioactivity & Radiobiology (Martindale’s Reference Desk)
atom : the smallest particle of an element that can exist either alone or in combination — Webster
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
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
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.
- The remarkable variability of actinide...on October 8, 2021 at 12:48 pm
Scientists have synthesized tetrafluoride powders of four radioactive elements—thorium, uranium, neptunium, and plutonium. These four elements are actinides, a series of heavy and radioactive elements. Tetrafluoride powders are simply powders with four fluoride atoms per atom of actinide. In this new study, scientists probed the magnetic fields of these powders. This revealed remarkable variations in the electronic structures of the powders even though they have nearly identical crystal […]
- New finding could inform how zeolites are used in...on October 7, 2021 at 1:54 pm
Zeolites could be considered as nature's workhorse.
- Nobel in chemistry honors 'greener' way to build...on October 6, 2021 at 9:56 am
Two scientists won the Nobel Prize in chemistry Wednesday for finding an ingenious and environmentally cleaner way to build molecules—an approach now used to make a variety of compounds, including medicines and pesticides.
- Process leading to supernova explosions and...on October 5, 2021 at 9:21 pm
A promising method for producing and observing on Earth a process important to black holes, supernova explosions and other extreme cosmic events has been proposed by scientists at Princeton University's Department of Astrophysical Sciences, SLAC National Acceleraor Laboratory, and the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL). The process, called quantum electrodynamic (QED) cascades, can lead to supernovas—exploding stars—and fast radio bursts that equal […]
- Metallic complexes made from cyclic moleculeson October 5, 2021 at 2:00 pm
In polymetallic complexes, two or more metal atoms combine with organic molecules into larger, complicated molecular structures. Such complexes are used in the development of e.g. new catalysts, molecular magnets and sensors. In the past, polymetallic complexes were often synthesized by the trial-and-error method of mixing metal ions with organic ligands, resulting in unpredictable compounds. The modern approach involves macrocycles: organic molecules having a ring-structure. The inside space […]