How can the number of atoms of an individual element be determined by usung a chemical formula?

1 Answer


The subscripts give the number of atoms of a particular atom.


In #BaCl_2# there is no subscript next to the #"Ba"#, so the number of atoms of barium
is 1. There is a subscript of 2 next to the chlorine, so the number of chlorine atoms is 2.

If there is a polyatomic ion, it is necessary to multiply the subscript of the polyatomic ion by the subscript of atoms in the polyatomic ion.

In #Fe_2(CO_3)_3# the number of iron atoms is two because of the subscript next to it. The number of carbon atoms is 3 #(1 xx 3 = 3)#. The number of oxygen atoms is 9 (#3 xx 3 =9 )#.

To find the number of the individual atoms in a molecular formula look at the subscripts and pay attention to the math.