Final answer:
Ionic bonds are formed through the transfer of electrons between atoms, resulting in charged ions. Magnesium and oxygen, as well as calcium and iodine, would form ionic bonds. Option a and d are correct.
Step-by-step explanation:
Ionic bonds are formed when there is a transfer of electrons from one atom to another, resulting in the formation of charged particles called ions. In an ionic bond, one atom loses electrons to become a cation (a positively charged ion), while the other atom gains electrons to become an anion (a negatively charged ion).
Based on this, the following pairs would form an ionic bond:
a) Magnesium and oxygen: Magnesium will lose two electrons and become Mg2+, while oxygen will gain two electrons and become O2-. The resulting compound is magnesium oxide (MgO). d) Calcium and iodine: Calcium will lose two electrons and become Ca2+, while iodine will gain one electron to become I-. The resulting compound is calcum iodide (CaI2).