Get yourself a Periodic Table; you should have one to hand if you are doing your homework, and have a gander at its structure. Calcium is a fourth Period metal, to the left of the Table as we face it. Chlorine is a 3rd Period non-metal towards the right of the Periodic Table.
It is a fact that ACROSS a Period, from left to right as we face the Table, atomic size decreases. The added electrons do not effectively shield the increasing nuclear charge, and atomic radii decrease. Down a Group, a column, of the Periodic Table, atomic size INCREASES, as a filled electronic shell tends to shield nuclear charge effectively. This contest between