How To Write The Chemical Formula And Chemical Names Of Ionic Compounds Page 2

The Criss-Cross Method

An alternative way to find the chemical formulas (easier way) is to use the criss-cross rule

It replaces the steps 1, 3, 4 from above!

Using the example above, the compound formed by calcium and iodine:

STEP 1: write the ionic charges above the symbols.

STEP 2: criss-cross the numbers using them as subscripts.

STEP 3: get rid of any “1’s” as the subscript. And be sure to “simplify” any subscripts if

necessary.

Example 2: What is the chemical formula and name of the ionic compound formed by aluminum

and sulphur?

Method #1

Criss-Cross Method

Example 3: What is the chemical formula and name of the ionic compound formed by beryllium

and oxygen?

Method #1

Criss-Cross Method

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