Use the periodic table to determine how many atoms of phosphorus (P) are in a sample that has a mass of 172.90 g.

Phosphorus has a molar mass of about 30.97 g/mol. The sample contains 172.90 ÷ 30.97 ≈ 5.583 mol of phosphorus atoms. Multiplying by Avogadro’s number gives 5.583 × 6.022 × 10²³ ≈ 3.36 × 10²⁴ atoms, so the correct choice is 3.36 × 10²⁴ atoms.

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