Astrophysics (Index)About

mass number

(atomic mass number, nucleon number)
(number of nucleons in an atomic nucleus)

An element isotope's mass number (or atomic mass number or nucleon number) is the number of nucleons (protons and neutrons) in its nucleus, the element's particular isotope being defined as those with nuclei that have this particular mass number. It approximates an atom's or nucleus's mass (using the mass of a nucleon as a mass unit), but the actual mass differs due to binding energy and for an atom, due to its electrons. The mass number can be indicated by a superscript to the left of the element's symbol, e.g., for the carbon (C) isotope with mass number 12, as 12C.


(chemistry,physics)
Further reading:
http://en.wikipedia.org/wiki/Mass_number

Referenced by pages:
alpha capture
Avogadro's number (NA)
Big Bang nucleosynthesis (BBN)
beta decay
calcium (Ca)
carbon (C)
element
fusion
helium (He)
iron (Fe)
isotope
lithium (Li)
lanthanide (Ln)
magnesium (Mg)
mass
neon (Ne)
neutron drip
nitrogen (N)
nucleon
nuclide
oxygen (O)
1H
radioactive decay
r-process
silicon (Si)
sodium (Na)
s-process

Index