Gram atomic mass -- what exactly is it?

Click For Summary

Discussion Overview

The discussion centers around the concept of gram atomic mass, exploring its definition, relationship to atomic mass and molar mass, and the terminology used in chemistry. Participants examine the implications of these definitions and their usage in different contexts, including potential confusion arising from the terms.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants express confusion over the definition of gram atomic mass, questioning whether it refers to the mass of one atom or one mole of an element.
  • It is noted that the gram atomic mass of sodium is 23g, which leads to questions about the size of this number in relation to atomic mass.
  • Some participants argue that the units are designed such that the numerical value of atomic mass in atomic mass units (a.m.u.) is equivalent to the mass of one mole of the element in grams.
  • There is a discussion about the nature of atomic mass units, with some participants stating that it is defined relative to the C-12 isotope.
  • One participant suggests that both the molar mass and atomic mass yield the same numerical value, indicating that the definitions are equivalent but chosen for clarity.
  • Another participant mentions that "gram-atom" is an outdated term for a mole, reinforcing the equivalence between gram atomic mass and molar mass.

Areas of Agreement / Disagreement

Participants generally agree that gram atomic mass and molar mass are equivalent in numerical value, but there is disagreement about the clarity and appropriateness of the terminology used. The discussion remains unresolved regarding the implications of these definitions and their usage.

Contextual Notes

Some participants highlight that the concept of an "atom of the element" is complicated by the presence of isotopes, which may affect the definition of atomic mass.

Hamiltonian
Messages
296
Reaction score
193
TL;DR
Is gram atomic mass, atomic mass(of an element) represented in grams, or the mass of one mole of an element
It is stated that the gram atomic mass of an element is its atomic mass represented in grams. The gram atomic mass of sodium is said to be 23g (isn't this number way to big to represent the mass of an atom?!) but if its the mass of one mole of sodium it makes sense(but won't that be molar mass). I searched it up and I kept seeing both definitions used interchangeably so I am not too sure which is correct.
 
Chemistry news on Phys.org
Yes, there is a lot of lousy wording, but units are selected in such a way that exactly the same number depicts mass of one mole of element expressed in grams and mass of one atom of that element expressed in a.m.u.

(actually for most elements there is no such thing as a well defined 'atom of the element', as they are mixtures of isotopes)
 
Borek said:
Yes, there is a lot of lousy wording, but units are selected in such a way that exactly the same number depicts mass of one mole of element expressed in grams and mass of one atom of that element expressed in a.m.u.

(actually for most elements there is no such thing as a well defined 'atom of the element', as they are mixtures of isotopes)
so the magnitude of the atomic mass unit of an element is always equal to the mass of one mole of that element in grams?
 
Yes, that's why a.m.u. has such a random value, it is just 1g/NA.
 
Borek said:
Yes, that's why a.m.u. has such a random value, it is just 1g/NA.
Isn't the a.m.u of an element given relative to the C-12 isotope which is assigned 12 a.m.u hence the value of ##1a.m.u = 1.66*10^{-27}##Kg
 
Actually it is a bit like asking what was first - an egg, or a hen? Both approaches are equivalent and both produce the same result - molar mass in grams and atomic mass in amu are the same number. The definition was chosen as the primary just for clarity, not because it is more fundamental than the other approach.
 
  • Like
Likes   Reactions: Hamiltonian
"Gram-atom" is an old-fashioned term for what we call a mole. It is equal to the relative atomic mass in grams (relative to H = 1 in the old days, I suppose) - not the mass of one atom. So 1 gram-atom of sodium is 23 g - the same as 1 mole. So the gram atomic mass is the same thing as the molar mass.
 
  • Like
Likes   Reactions: epenguin and Hamiltonian

Similar threads

  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 24 ·
Replies
24
Views
6K
Replies
1
Views
2K
Replies
2
Views
2K
Replies
2
Views
6K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
1
Views
4K
  • · Replies 7 ·
Replies
7
Views
3K