Question

The element a belongs to 13 group of periodic table what is the chemical formula of its chloride

Answer 1

The element a belongs to 13th group of the periodic table has valency 3.and chloride has valency 1.

so ,by cross multiplication we get the formula of chloride=  MCl3  

where M is the assumed element of group 13.

Answer 2

Answer: for eg.

AlCl3

Explanation:

We know that aluminum has a valency of +3 because it has three valence electron which it can lose easily. Similarly, chlorine has a valency of −1 because it can gain an electron.

So in writing the formula, there is a cross of the two valencies because three chlorine atoms will have to react with one aluminium atom to gain one electron each.  

[Al]3++3[Cl]−→AlCl3