mass number
(A, 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, typically indicated by symbol A)
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 in units of the
mass of a nucleon,
but this is not exact because the mass of a proton differs slightly
from the mass of a neutron, and also, different isotopes incorporate
different amounts of binding energy to hold the nuclei together.
Also, 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., 12C
for the carbon (C) isotope with mass number 12.
(chemistry,physics)
Further reading:
https://en.wikipedia.org/wiki/Mass_number
http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/atom.html
http://www.chem.uiuc.edu/rogers/Text4/Tx42/tx42.html
https://www.wlwv.k12.or.us/cms/lib/OR01001812/Centricity/Domain/1338/NOTES%20-%204.3_Atomic_Mass_Isotopes_2017_slideshow.pdf
Referenced by pages:
1H
alpha capture
aluminum (Al)
Avogadro's number (NA)
beta decay
Big Bang nucleosynthesis (BBN)
calcium (Ca)
carbon (C)
element
fusion
helium (He)
hydrogen (H)
iron (Fe)
isotope
lanthanide (Ln)
lithium (Li)
magnesium (Mg)
mass
neon (Ne)
neutron drip
nickel (Ni)
nitrogen (N)
nucleon
nuclide
oxygen (O)
phosphorus (P)
r-process
radioactive decay
s-process
silicon (Si)
sodium (Na)
sulfur (S)
titanium (Ti)
Index