Explain how to write a formula for an ionic compound given the names of the metal and nonmetal (or polyatomic ion) in the compound.

+2 votes
asked May 25, 2012 in General Chemistry by Gummmys ~Expert~ (1,105 points)

1 Answer

+2 votes
Best answer
Some basic rules:

Ionic compounds always contain a positve and negative ions.

The sum of the charges (the postive and negative charges) must be equal.

The formula is in simplest whole number ratio form.


First step is to write the metal followed by its charge.

Next write the nonmetal with its charge. (charges can be found based on element group on periodic table)

Then balance out the compound according to the charges until it is electrically neutral. This is where you look at the charges on each ion, and multiply the metals and nonmetals accordingly so that the charges add up to zero.

answered May 26, 2012 by kirby ~Expert~ (3,020 points)