Talk:Atomic mass

Persistent Confusion on Relative Atomic Mass
I have once again corrected the persistent confusion on relative atomic mass. The most important point to remember is that relative atomic mass is practically an antonym of atomic mass. Relative atomic mass is a weighted average and atomic mass is not. I know this is very confusing but please read definitions carefully and make sure you understand the differences.

Correct statement:

Relative atomic mass is a synonym of atomic weight.

Incorrect Statement:

Relative atomic mass and relative isotopic mass are essentially the same.

Why: The relative atomic mass is a weighted average. The relative isotopic mass is not.

Incorrect Statement:

Relative atomic mass and atomic mass are essentially the same.

Why: The relative atomic mass is a weighted average. The atomic mass is not.

Incorrect statement:

The mass defect of all atomic masses above C12 are positive.

Why: They are in fact mostly negative and only become positive at high Z and low Z. The error here is in the confusion between mass defect of atoms and the atomic weights (or more precisely the standard atomic weights) that mostly have masses slightly above the nominal atomic weight. This trend in the decimal places of the atomic weights has to do the relative prevalence of heavier isotopes at higher Z and has little to do with mass defect due to nuclear binding energies.

--Nick Y. (talk) 18:33, 22 September 2009 (UTC)


 * I find the objections above all correct, and hopefully they have all been fixed in the present version of the article. S  B Harris 23:49, 10 October 2014 (UTC)

Stylized lithium-7 atom?
The picture of the Stylized lithium-7 atom has (3) electrons each at equal distance orbit from the nucleus, which seems misleading. Is there a case in real life where you could force all (3) electrons in lithium-7 to have equal energy and be stable in a single electron shell? Even in the bohr model, you'd expect (2) shells, not a single shell. A picture of a Quantum model of lithium-7 I think would be better. Or at least a picture showing (2) electron shells... Goslackware (talk) 17:27, 4 October 2023 (UTC)


 * The Pauli exclusion principle says definitely no. However the electronic structure of the atom is not relevant to this particular article, and a more accurate diagram might get in the way of the intended meaning. FChlo (talk) 01:27, 16 January 2024 (UTC)

Explain jargon: numbers in parenthesis
I noticed numbers in parenthesis, for example "$1.008$". What does that (14) part mean? It's not a common way to write numbers, so it should be explained. Mateussf (talk) 12:39, 19 June 2024 (UTC)