Answer:
The valency of calcium is +2
Step-by-step explanation:
Calcium is in group two. The members of group two are divalent metals that loose two electrons to form M^2+.
Since they form M^2+, they form ionic bonds with two uninegative ions. Chlorine is in group 17. This implies that its valency is -1 and it accepts one electron when it participates in an ionic bond.
Hence it will take two chlorine atoms to receive two electrons from one calcium atom in an ionic bond making the ratio of calcium to chlorine in the compound 2:1.