Confusion with definitions of mass What is the difference between:
atomic mass
relative atomic weight
relative isotopic weight
standard atomic weight
atomic weight
relative atomic mass
I am told by Wikipedia that:
relative atomic weight = atomic weight
and a the start of the article it says:
For a single given sample, the relative atomic mass of a given element is the weighted arithmetic mean of the masses of the individual atoms (including their isotopes)
so standard atomic weight = relative atomic weight
But at https://en.wikipedia.org/wiki/Relative_atomic_mass#Standard_atomic_weight#Definition it says:
It is a synonym for atomic weight, though it is not to be confused with relative isotopic mass. Relative atomic mass is also frequently used as a synonym for standard atomic weight and these quantities may have overlapping values if the relative atomic mass used is that for an element from Earth under defined conditions. However, relative atomic mass (atomic weight) is still technically distinct from standard atomic weight because of its application only to the atoms obtained from a single sample; \textbf{it is also not restricted to terrestrial samples, whereas standard atomic weight averages multiple samples but only from terrestrial sources}
I am told here that:
The standard atomic weight (Ar, standard) of a chemical element is the weighted arithmetic mean of the relative atomic masses (Ar) of all isotopes of that element weighted by each isotope's abundance on Earth.
But in this video I am told this is the definition of relative atomic mass.
Here I am told:
Atomic mass (ma) is the mass of an atom. A single atom has a set number of protons and neutrons, so the mass is unequivocal (won't change) and is the sum of the number of protons and neutrons in the atom.
Atomic weight is a weighted average of the mass of all the atoms of an element, based on the abundance of isotopes. The atomic weight can change because it depends on our understanding of how much of each isotope of an element exists.
In other words:
Atomic weight = standard atomic weight
Also, which of these definitions is used to convert grams of a substance into moles
Relative Atomic Mass vs Atomic Weight
Relative Atomic mass ($m_a$) is the measurement of the mass of an atom relative to carbon-12. It's dimension is M.[1] It can be measured in Da/u, kg or g.* [3]
$$m_a \approx \mathrm{Mass\ Number} \times {1\ \mathrm{u}}$$
except for carbon-12 where they are the same.
Atomic weight is:
Relative atomic mass vs Standard atomic mass
Relative atomic mass or Relative atomic weight is the weighted average of the isotopes of an element according to their abundance in a given sample compared to the atomic mass of carbon-12. It's dimension is M/M or 1. [2] [4]
Standard atomic mass is the same except that the samples are restricted to terrestrial samples normally considering/averaging results from many different samples or results given by the CIAAW.
Relative Isotopic Mass vs Relative Atomic Mass
Relative Isotopic mass considers the mass of an isotope compared to the atomic mass of carbon-12. This is also dimensionless.
*Universal mass constant vs kg , g ,etc
The universal mass constant ($m_u$) is defined as $\frac{1}{12}$ of the mass of carbon-12 which defines 1 Da or 1 u. All measurements in Da are comparisons to the mass of a carbon-12 atom. Since the discovery of Avogadro's constant, we know: [3]
$$ 1\ {\rm{Da}} = 1.660\ 539\ 066\ 60(50)\times 10^{-27}\ \mathrm{kg}$$
Molar Mass vs Molecular Mass (or Formula Mass)
Molar Mass is the grams of a substance in 1 mole of it measured in gram per mole. It's dimension is $\mathbf{M N^{-1}}$.
Molecular mass or molecular weight is the sum of the atomic masses of all the component atoms of each element measured in u. It's dimension is M. Formula mass or formula weight is the sum of the atomic masses of component ions (not sure of the difference between this and molecular mass - in terms of quantity).[2]
[1] see the answer to this Q by M Farooq
[2] What is the difference between &quot;molecular mass&quot;, &quot;average atomic mass&quot; and &quot;molar mass&quot;?
[3] Mass number, (relative) atomic mass, average mass
[4] Quick and simple explanation of molar mass, molecular mass and atomic mass