Question

Using the periodic table predict formula of compound formed between an element ‘X’ of group 2 and another element of group 17.

Answer 1

1. The element X belongs to group 2. So, the number of valence electrons are 2 and its valency is 2. 

2. The element Y belongs to group 17 or VII. So, the number of valence electrons are 7 and its valency = 8 – 7= 1. 

3. During formation compound elements exchange their valencies. 

∴ The formula of compound is XY₂.