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Arsenic is also found in food, water, soil, and air. [132] Arsenic is absorbed by all plants, but is more concentrated in leafy vegetables, rice, apple and grape juice, and seafood. [133] An additional route of exposure is inhalation of atmospheric gases and dusts. [134]
Arsenic (33 As) has 32 known isotopes and at least 10 isomers. Only one of these isotopes, 75 As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73 As with a half-life of 80 days.
The electron configuration is determined by the charge of the nucleus, which is determined by the number of protons, or atomic number. The number of neutrons is the neutron number. Neutrons do not affect the electron configuration. Atoms of a chemical element that differ only in neutron number are called isotopes.
The neutron number (symbol N) is the number of neutrons in a nuclide. Atomic number (proton number) plus neutron number equals mass number : Z + N = A . The difference between the neutron number and the atomic number is known as the neutron excess: D = N − Z = A − 2 Z .
Aston discovered the whole number rule, that the masses of all the particles have whole number relationships to oxygen-16, [18] which he took to have a mass of exactly 16. [4] (Today the whole-number rule is expressed in multiples of an atomic mass unit (amu) relative to carbon-12. [19]). Significantly, the one exception to this rule was ...
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in a process called Big Bang nucleosynthesis. [1]
The mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), [1] also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in atomic mass units.
The number of unstable nuclides discovered has grown, with about 3000 known in 2006. [ 55 ] The most common and consequently historically the most important forms of natural radioactive decay involve the emission of alpha-particles, beta-particles, and gamma rays.