Chapter 2 - Chemical Compounds - Questions for Review and Thought - Applying Concepts - Page 90f: 123a

1 mol of $Cl_2$ has the greater number of atoms.

1 mol of $Cl$: 1 mol of $Cl$ = 1 mol of atoms. 1 mol of $Cl_2$: 1 $Cl_2$ molecule has 2 $Cl$ atoms; therefore, 1 mol of $Cl_2$ has 2 moles of $Cl$ atoms. 2 moles of atoms > 1 mol of atoms. 1 mol $Cl_2$ > 1 mol $Cl$