Na+ has completely filled K and L shells. Explain.

A sodium ion Na+, has 10 electrons in it. Now, the maximum capacity of K shell is 2 electrons and that of L shell is 8 electrons. Taken together, the maximum capacity of K and L shells is 2 + 8 = 10 electrons. A sodium ion Na+ has completely filled K and L shells because its 10 electrons can completely fill up K and L shells.