How does calcium obey the octet rule when reacting to form ionic compounds?

• A. Calcium gains two electrons to complete its valence shell.
• B. Calcium does not change its electron configuration when forming compounds.
• C. Calcium shares electrons equally with other atoms to reach eight valence electrons.
• D. Calcium loses two electrons to achieve a stable noble gas electron configuration.

Answer: (D)

Verified step by step guidance

1. Understand the octet rule: atoms tend to gain, lose, or share electrons to have eight electrons in their valence shell, achieving a stable noble gas configuration.
2. Identify calcium's position in the periodic table: calcium is an alkaline earth metal in group 2, meaning it has 2 valence electrons.
3. Determine how calcium achieves the octet: since calcium has 2 valence electrons, it tends to lose these electrons rather than gain six, because losing 2 electrons results in a full octet in the previous shell.
4. Recognize that when calcium loses 2 electrons, it forms a Ca^{2+} ion with the electron configuration of the noble gas argon, thus obeying the octet rule by electron loss.
5. Conclude that calcium forms ionic compounds by losing two electrons to nonmetals, which gain electrons, resulting in stable ionic bonds and fulfilling the octet rule.