Lesson -- intro to ionic names formulas

​You have learned how electrons move from one atom to another to form ionic bonds.
In the picture, oxygen is becoming an ion.
Oxygen is in Group 6, so it already has 6 valence e-
To become an ion, it takes 2e-
But lithium atoms only have 1e- to give, so another lithium atom is needed for oxygen to have a full 8e- shell.

​The formula for this compound is
Li₂O

Remember this assignment?

Criss-cross Method

Rule #1.
Do not write charges.

Rule #2. Same numbers cancel

Roman Numerals