Question

What are the various letters used by Bohr to represent electron shells in an atom?

Answer 1

All the shells are represented by letters called K, L, M, N, O, P shells.

These shells accommodate different number of valence electrons depending on the chemical properties of that element. For example,

Hydrogen has atomic number 1. So the valence electrons in the shells are represented as : K - 1
Sodium has atomic number 11. So it will be represented as K - 2, L - 8, M - 1

So all the shells are represented with different alphabets. Also the number of electrons that can be accommodated in a shell can be given by the formula 2n², where n represents the number of shells.