Determining formulas for ionic compounds

The (+) and (-) charges must cancel each other to make a neutral compound.

Mg+2 and Cl-1 make MgCl2

Because you need 2 Cl- to cancel the +2 charge on Mg

What is the formula for a compound of Al and O?

Al+3 O-2

What is the formula for a compound of Al and O?

Al+3 O-2

Find the least common multiple 3+ X 2 = 6+ 2- X 3 = 6-

Al2O3

A force can shatter an ionic crystal.