Calcium chloride contains calcium and chloride ions. write the ground-state electron configuration for the chlorine ion.

The electron configuration of an atom of Chlorine Cl (neutral Chlorine) is:

1s2 2s2 2p6 3s2 3p5

Now if the Chlorine becomes an ion, it becomes Cl-. So we can see that 1 electron is added therefore the new electron configuration is:

1s2 2s2 2p6 3s2 3p6