What is the correct formula for barium chlorate?

1 Answer
Nov 9, 2016

Answer:

#"Ba(ClO"_3)_2"#

Explanation:

The barium cation has the formula #"Ba"^(2+)"#. The chlorate polyatomic anion has the formula #"ClO"_3"^(-)#.

An ionic compound is neutral, which means that its overall charge is #0#. Since the barium ion has a charge of #2^(+)#, the negative charge will have to be #2^-#. We can't change the formula or charge of the chlorate ion, but we can change the number of chlorate ions. Two chlorate ions will have a charge of #2^(-)#. So the formula for barium chlorate is:

#"Ba(ClO"_3)_2"#

Now the formula represents a neutral compound. Notice that because there are two chlorate ions, which are polyatomic, we put the formula for the chlorate ion in parentheses with a subscript of #2#.

There is a method for writing formulas for ionic compounds which is called the crisscross rule. The following video explains how it works.

If you're not sure how to determine the charge of a monatomic ion from the periodic table, the following video should be helpful.