The formula for the compound formed from calcium and oxygen is CaO.
This compound is known as calcium oxide. To understand why, we need to look at the charges of the ions involved in the formation of this compound. Calcium (Ca) is an alkaline earth metal found in Group 2 of the periodic table, and it has a tendency to lose two electrons to achieve a stable electron configuration, resulting in a +2 charge (Ca2+). On the other hand, oxygen (O), which is in Group 16, tends to gain two electrons to fill its outer electron shell, resulting in a -2 charge (O2-).
When calcium and oxygen react, these ions combine in a 1:1 ratio to neutralize each other’s charges. Therefore, the chemical formula for the compound formed is CaO. This simple ratio reflects the complete transfer of electrons from calcium to oxygen, creating a stable ionic compound.