Question

Why the name of atomic shell starts with K not A? ​

Answer 1

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.