Which number indicates the number of atoms of each element in a molecule of a substance

To indicate the number of atoms of each element present in a molecular compound, scientists use -

What is the empirical formula for a compound if a sample contains 3.72 g of P and 21.28 g of Cl?

In [Cu(NH₃)₄]²⁺, the subscript 4 indicates which of the following?

What is the empirical formula of a compound that is 40% sulfur and 60% oxygen by weight?

7 graham crackers, 6 pieces of chocolate, and 5 marshmallows

A chemist wishing to identify a compound determines the masses of its elements as: 1.445 g S and 6.391 g Cl. Determine its empirical formula.