Question

Na${}^{+}$ has completely filled K and L shells. Explain.

Answer 1

An atom of Na has a total of 11 electrons. Its electronic configuration is 2, 8, 1. But, Na${}^{+}$ ion has one electron less than Na atom i.e. it has 10 electrons. Therefore, 2 electrons go to K-shell and 8 electrons go to L-electrons, thereby completely filling K and L shells.