photo.jpg

# Example 1 - To find formula for sodium oxide, - Sodium = Group 1 = ion is Na+ - Oxygen = Group 6 = ion is O2- We want equal amount of pos & neg charges, we need 2 sodiums to give 2 pos, charges to activate cancel the neg ones on the oxygen So you need: Na+, Na+, O2- The formula is: Na2O # Example...

# Example 1 - To find formula for sodium oxide, - Sodium = Group 1 = ion is Na+ - Oxygen = Group 6 = ion is O2- We want equal amount of pos & neg charges, we need 2 sodiums to give 2 pos, charges to activate cancel the neg ones on the oxygen So you need: Na+, Na+, O2- The formula is: Na2O # Example 2 To find formula for barium lead nitrate: - Barium = Group 2 = Ba2+ ion - Nitrate = NO3 = (N=Group 3-, O = Group 2-) We need it to be equal pos/neg charge, so we need: 2 nitrate ions for each barium Formula = Ba(NO3)2 (Must be in brackets) Barium ions