The number of atoms in 3 moles of sodium (Na) can be calculated using Avogadro's number (Nₐ), which is approximately 6.022 x 10^23 atoms per mole.

Number of atoms = Number of moles × Avogadro's number

Number of atoms in 3 moles of Na = 3 moles × 6.022 × 10^23 atoms/mole

Number of atoms in 3 moles of Na = 18.066 × 10^23 atoms

Therefore, there are 18.066 x 10^23 atoms of sodium in 3 moles of Na.

Mass:

The mass of 3 moles of sodium can be calculated using its molar mass (M). The molar mass of sodium is 22.99 grams per mole (g/mol).

Mass = Number of moles × Molar mass

Mass of 3 moles of Na = 3 moles × 22.99 g/mol

Mass of 3 moles of Na = 68.97 grams

Therefore, the mass of 3 moles of sodium is 68.97 grams.