Final answer:
The correct Lewis symbol for the calcium ion is Ca⁺² option (a) indicating it is a cation with a +2 charge, and when combined with a sulfide ion, the formula of the compound is CaS.
Explanation:
The correct Lewis symbol for the calcium ion is Ca⁺² which signifies that the calcium atom has lost two electrons to form a cation with a +2 charge. Calcium ions are represented as having a +2 charge because, upon losing two electrons, the balance between protons (positively charged) and electrons (negatively charged) is disrupted, resulting in more protons than electrons.
This creates a positively charged ion, hence the notation Ca⁺². When calcium forms a compound with another ion, such as the sulfide ion (S²⁻), the resulting compound formula would be CaS as the charges of the two ions will balance each other out.