Question

iii] For the above element ie. potassium why does the ‘M shell' not have ten
electrons, even though the maximum number of electrons which can be
present in the M shell are eighteen.

**no copyright answers*​

Answer 1

The atomic no. of potassium (K) is 19.

So the electronic configuration of potassium is as follows :

K L. M N

2 8. 8. 1

Now, K shell can accomodate maximum 2 electrons. So there are 2. L shell can accomodate at most 8 electrons. So there are 8.

Other than this 2n^2 law , there another law for electronic configuration. It states that 'The outermost shell of an atom can hold a maximum of 8 electrons.'

So, after filling K and L shell, we are left with 9 electrons, But, if M shell holds the last 9 electrons, then it will violate the above law. So, after filling the M shell with 8 electrons (which is maximum possible), we have to introduce N shell for holding the extra 1 electron.

Hope your doubt is clarified.

Thanks !!