Which quantum number is to be mentioned to distinguish between the electrons present in the K-shell?

Explanation

For K-shell (n=1), l=0 and m=0. this indicates that K=shell has only one orbital and this orbital can accommodate a maximum of 2 electrons having spin quantum no, 's' with values +1/2 and -1/2. so, to distinguish between the two electrons in the K-shell, it is important to indicate their spin quantum numbers.