How does the mole relate to atoms, molecules and ions?

Mar 24, 2016

A mole is simply a quantity of $6.022 \times {10}^{23}$ of anything. We can have a mole of atoms, molecules, ions... or elephants.

One mole of atoms of an element has a mass equivalent to the 'mass number' (now sometimes called 'nucleon number') of that element, e.g. 1 mole of ""_6^12C has a mass of $12$ $g$.

Explanation:

Technically it's slightly more complex than the answer above, because different isotopes have different mass numbers and abundances.

Carbon is mostly ""_6^12C, with very small amounts of ""_6^13C and ""_6^14C, so the relative atomic mass of naturally occurring carbon is very close to $12$ gmol^-1.

On the other hand, naturally occurring chlorine is about $\frac{3}{4}$ ""_17^35Cl and about $\frac{1}{4}$ ""_17^37Cl#, so the relative atomic mass of naturally occurring $C l$ is about $35.5$.