Chapter 2 Atoms, Molecules, and Ions - Study Questions - Page 95f: 106

$3.2\times10^{-4}\ mol$ $1.9\times10^{20}\ atoms$

Atomic weight (g/mol): $Fe: 55.845$ Number of moles: $18\times10^{-3}\ g \div 55.845\ g/mol = 3.2\times10^{-4}\ mol$ Number of atoms: $3.2\times10^{-4}\ mol \times 6.022 \times 10^{23}\ atom/mol = 1.9\times10^{20}\ atoms$