1.- The
metal ion is always positive and is written first.
2.- The
non-metal ion is always negative and is written second.
3.-Write
the ionic charge above each symbol bases on the number of electrons gained or
lost to become stable.
4.-
Crisscross the numbers, drop the signs and write them together.
Example:
a) Al and S
1.- Al
2.- S
3.- Al3+ S2-
4.-Crisscross Al2S3
b) Na and O
1.- Na
2.- O
3.- Na+ O2-
4.- Crisscross
Na2O
