And so #"1 mole"# of lithium specifies #6.02214xx10^23# individual lithium atoms, and this has a mass of #6.94*g#; i.e. we quote the equivalent mass of lithium metal as #6.94*g*mol^-1#. This concept of equivalence is one of the most important to grasp in chemistry.
For the reaction......
#2Li(s) + 1/2O_2(g) rarr Li_2O#
If approx. #14*g# of lithium reacts, how many oxygen molecules react, how many formula units of lithium oxide result, and what is the mass of lithium oxide?