Question

The first shell of an atom should contain 2 electrons and the 2nd should have 8 electrons and the third shell should have 18 electrons and the next shell should have 32 electrons but why do we write the electronic configuration of Ca as 2,8,8,,2 and why we dont write it as 2,8,10

Answer 1

we donot it as 2,8,10 because 2 electrons are present in k shell,next 8 electrons are present in L shell and the next 8 electrons are in M shell.But, last two electrons which are valency electrons are present in N shell.To vary those N shell electrons from M shell electrons, we write as 2,8,8,2.