The property that relates number of moles and mass of an atom is the atomic weight. For atoms, we can consult the atomic weight in a periodic table, for example.
Consulting the atomic weight of aluminium, we get:
[tex]W_{Al}\approx26.98g/mol[/tex]The relationship is as follows:
[tex]W_{Al}=\frac{m_{Al}}{n_{Al}}[/tex]Solving for n and substituting the given mass and the consulted atomic weight, we get:
[tex]\begin{gathered} n_{Al}=\frac{m_{Al}}{W_{Al}} \\ n_{Al}=\frac{216g}{26.98g/mol}\approx8.0mol \end{gathered}[/tex]So, there is approximately 8 mol in 216 g of aluminium.
