1. Sodium (Na)

* Molar mass of Na: 22.99 g/mol

* Moles of Na: 64 g / 22.99 g/mol = 2.78 mol

* Number of Na atoms: 2.78 mol * 6.022 x 10^23 atoms/mol = 1.67 x 10^24 atoms

2. Nitrogen (N)

* Number of Nitrogen atoms: 3 mol * 6.022 x 10^23 atoms/mol = 1.81 x 10^24 atoms

Therefore:

* There are approximately 1.67 x 10^24 atoms in 64 g of Na.

* There are approximately 1.81 x 10^24 atoms in 3 moles of nitrogen atoms.