Counting Atoms in Formulas

Count the atoms of each element in the following formulas. Remember that the subscript following the symbol for the element tells that number of atoms of that element in the formula. No subscript means there is one atom of the element present. Subscripts outside the parenthesis refer to the number of groups of atoms present is a formula. Therefore, the subscript outside the parenthesis is multiplied by the subscripts inside the parenthesis.

For example, Cr2(SO4)3 contains 2-Cr,3-S and 12-0 atoms.