Mass nummer

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The mass nummer (A), an aa cried atomic mass nummer or nucleon nummer, is the tot nummer o protons an neutrons (thegither kent as nucleons) in an atomic nucleus. Acause protons an neutrons baith are baryons, the mass nummer A is identical wi the baryon nummer B as o the nucleus as o the whole atom or ion. The mass nummer is different for each different isotope o a chemical element. This is nae the same as the atomic nummer (Z) which denotes the nummer o protons in a nucleus, an sicweys uniquely identifies an element. Hence, the difference atween the mass nummer an the atomic nummer gies the nummer o neutrons (N) in a gien nucleus: N=A−Z.[1]

The mass nummer is written aither efter the element name or as a superscript tae the left o an element's seembol. For ensaumple, the maist common isotope o carbon is carbon-12, or 12
, which haes 6 protons an 6 neutrons. The full isotope seembol wad an aa hae the atomic nummer (Z) as a subscript tae the left o the element seembol directly ablo the mass nummer: 12
.[2] This is technically redundant, as each element is defined bi its atomic nummer, sae it is eften omittit.

References[eedit | eedit soorce]

  1. "How many protons, electrons and neutrons are in an atom of krypton, carbon, oxygen, neon,platnum, gold, etc...?". Thomas Jefferson National Accelerator Facility. Retrieved 2008-08-27.
  2. "Elemental Notation and Isotopes". Science Help Online. Retrieved 2008-08-27.