Question

How to know which transiton is allowed which is not in group theory?

Answer 1

What you have answered is correct.

Groups are vertical columns of the periodic table. These groups consist of atoms with the same number of valence electrons. Due this electron configuration, groups all have similar chemistry.

Valence electrons - the number of electrons in the outer shell tells us in which group the element is present. We can use the below given group formula for the same.

 

For the s block element, group = number of valence electron.

For p block element, group = 10 + total number of valence electron.

For d block element, group = number of electrons in the (n-1) d sub shell and ns sub shell.