Calculate the number of phosphorus atoms in a 120.0g sample of diphosphorus pentoxide P2O5. Be sure your answer has a unit symbol if necessary, and round it to 4 significant digits.

2.546 * 10^23 atoms of P2O5

Explanation:

Number of moles in 120.0 g of P2O5 =mass/ molar mass = 120.0 g/283.886 g/mol= 0.423 moles

1 mole of P2O5 contains 6.02 * 10^23 atoms

hence 0.423 moles of P2O5 will contain 0.423 *  6.02 * 10^23 /1 = 2.546 * 10^23 atoms of P2O5

just did the assignment and the answer was #1 +2 n