Question

why does energy shells starts from K and not from A. like K L M N...​

Answer 1

Explanation:-

the electron shells begin being named with K, L, M, N, and not with A, B, ... because, that are emitted by atoms when they are hit with high energy electrons.

K denotes the first shell (or energy level), L the second shell, M, the third shell, and so on. In other words, the KLMN (OP) notation only indicates the number of electrons an atom has with each principal quantum number ( n ). The SPDF notation subdivides each shell into its subshells.

Answer 2

Answer:

As it turns out, the K type X-ray is the highest energy X-ray an atom can emit. It is produced when an electron in the innermost shell is knocked free and then recaptured. This innermost shell is now called the K-shell, after the label used for the X-ray. Barkla won the 1917 Nobel Prize for Physics for this work.