Why is calcium oxide CaO, and not CaO2?
The Correct Answer and Explanation is :
The correct answer is: consists of one calcium (Ca) atom and one oxygen (O) atom
Calcium oxide (CaO) consists of one calcium (Ca) atom and one oxygen (O) atom, forming a binary ionic compound. To understand why its formula is CaO instead of CaO₂, we need to explore the concepts of valence, oxidation states, and the nature of ionic compounds.
Calcium is an alkaline earth metal located in Group 2 of the periodic table. It has an atomic number of 20 and typically forms a +2 oxidation state by losing two electrons when it reacts. This +2 charge means that calcium tends to bond with two negative charges to achieve electrical neutrality.
Oxygen, on the other hand, is a nonmetal found in Group 16 and generally has a -2 oxidation state. This -2 charge arises from its tendency to gain two electrons to complete its outer electron shell, achieving a stable electronic configuration similar to that of noble gases.
When calcium and oxygen combine, the +2 charge from the calcium ion (Ca²⁺) and the -2 charge from the oxide ion (O²⁻) balance each other out, resulting in a neutral compound. Therefore, the simplest formula for this ionic compound is CaO, indicating one calcium ion for every one oxide ion.
If we were to consider a formula like CaO₂, it would imply that for every calcium atom, there are two oxygen atoms. In such a case, the resulting compound would have an overall charge of -2 (due to the two -2 charges from the two oxide ions), which does not balance with the +2 charge of calcium, leading to an unstable ionic compound.
In summary, the formula CaO represents a stable ionic compound formed from calcium and oxygen, ensuring charge neutrality, while CaO₂ would not be a valid representation for calcium oxide, as it would lead to an unbalanced charge. Thus, the correct chemical formula for calcium oxide is CaO.