Which one of the following will have the largest number of atoms?

The number of atoms is directly proportional to the number of moles and is inversely proportional to the molar mass. The molar masses of Au, Na, Li, and Cl2 are 197 g/mol, 23 g/mol, 7 g/mol, and 71 g/mol respectively. Since the molar mass of Li is minimum, it will have a maximum number of atoms.