Question

If there are three shells in an atom, what is the maximum number of electrons with them and why. Do by using 2n2 formula. Please do write the answer in brief way.​

Answer 1

Number of electrons associated with three shells using formula 2n² (here, n = number of shell) -

First shell (also named as 'K' shell) = 2(1)² = 2 electrons

Second shell (also named as 'L' shell) = 2(2)² = 8 electrons

Third shell (also named as 'M' shell) = 2(3)² = 18 electrons

But, the maximum capacity of a shell is to accommodate only 8 electrons except first shell. Only 2 electrons can be filled in first shell and 8 electrons in second, third and so on. This is because of the Octet rule.

Example :

Electronic Configuration of Calcium (₂₀Ca) = 2, 8, 8, 2

Electronic Configuration of Manganese (₂₅Mn) = 2, 8, 8, 7