Which sample contains the greater number of atoms, a sample of Li that contains 6.8 x 10^22 atoms or a 1.97 mole sample of Na?

                     1.97 moles of Na contains greater number of atoms than 6.8 × 10²² atoms of Li.

Explanation:

                    To solve this problem we will first calculate the number of atoms contained by 1.97 moles of Na and then will compare it with 6.8 × 10²² atoms of Li.

                    As we know that 1 mole of any substance contains exactly 6.022 × 10²³ particles which is also called as Avogadro's Number. So in order to calculate the number of atoms contained by 1.97 moles of Na, we will use following relation,

          Moles  =  Number of Atoms ÷ 6.022 × 10²³ atoms.mol⁻¹

Solving for Number of Atoms,

          Number of Atoms  =  Moles × 6.022 × 10²³ Atoms.mol⁻¹

Putting values,

          Number of Atoms  =  1.07 mol × 6.022 × 10²³ Atoms.mol⁻¹

          Number of Atoms  = 1.18 × 10²⁴ Atoms of Na

Hence,

          1.97 moles of Na contains greater number of atoms than 6.8 × 10²² atoms of Li.