A 48.0-g sample of an element has the same number of atoms as 6.00 g Na. What is the element?

Answer 1

mols Na = 6.00/23 = 0.261
atoms Na = 0.261 mols x (6.02 x 10^23 atoms/mol) = 1.57 x 10^23.

atoms element X = 1.57 x 10^23 (same as Na).
mols X = 1.57 x 10^23 x (1 mol/6.02 x 10^23 atoms) = 0.261
mols = g/atomic mass or rearrange to
atomic mass = g/mol = 48.0/0.261 = ??. Look it up on the periodic table.