sábado, 13 de octubre de 2012

Writing formulas for ionic compounds

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.

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