Which quantum number differs for the two electrons present in K-shell of an atom? — Atomic Structure Chemistry Question

💡 Solution & Explanation

The K-shell corresponds to the principal quantum number n = 1, which contains only the 1s subshell consisting of a single orbital. Since both electrons reside in this same 1s orbital, they share the identical principal (n=1), azimuthal (l=0), and magnetic (m=0) quantum numbers. According to Pauli's exclusion principle, they must have opposite spins (+1/2 and -1/2). Therefore, they differ in their spin quantum number (s).