Question 1
Use Mendeleev's periodic table to predict the formulae for the oxides of the following elements: K, C, Al, Si, Ba.
Valency of oxygen is 2.
K is in group 1 and has valency 1. Using criss-cross method:
Symbol: K O
↘↙
Valency: 1 2
Therefore,the oxide formed is: K2O.
C is in group 14 and has valency 4. Using criss-cross method:
Symbol: C O
↘↙
Valency: 2 4
Therefore, the oxide will be CO2.
Al is in group 13 and has valency 3. Using criss-cross method:
Symbol: Al O
↘↙
Valency: 3 2
Therefore, the oxide will be Al2O3.
Si is in group 14 and has valency 4. Using criss-cross method:
Symbol: Si O
↘↙
Valency: 4 2
Therefore, the oxide will be SiO2.
Ba is in group 2 and has valency 2. Using criss-cross method:
Symbol: Ba O
↘↙
Valency: 2 2
Therefore, the oxide will be BaO.