* Calcium's Outer Shell: Calcium (Ca) has two electrons in its outermost shell (the 4s shell). It wants to lose these two electrons to achieve a stable, full outer shell like the noble gases.
* Oxygen's Outer Shell: Oxygen (O) has six electrons in its outermost shell (the 2p shell). It wants to gain two electrons to also achieve a stable, full outer shell.
* The Reaction: When calcium and oxygen react, calcium readily loses its two outer electrons to become a positively charged calcium ion (Ca²⁺). Oxygen gains these two electrons, becoming a negatively charged oxide ion (O²⁻).
* Ionic Bond Formation: The oppositely charged ions are attracted to each other, forming an ionic bond. This attraction is what holds the calcium and oxygen together in the compound calcium oxide (CaO).
In summary: The outer shell of the calcium atom is emptied, and the two electrons are transferred to the oxygen atom, filling its outer shell. This results in the formation of a stable ionic compound.
