Directions: Count the number of atoms.

Ar

Co2

Na3PO4

SO3

NaC2H3O2

We have:

1 atom of Ar

2 atoms of O and 1 atom of C (3 atoms)

3 atoms of Na, 1 atom of P and 4 atoms of O (8 atoms)

1 atom of S and 3 atoms of O (4 atoms)

1 atom of Na, 2 atoms of C, 3 atoms of H, 2 atoms of O (8 atoms)