How does a calcium atom obey the octet rule when forming compounds?

• A. It gains two electrons to complete its valence shell.
• B. It loses two electrons to achieve a stable noble gas configuration.
• C. It shares electrons with other atoms to reach eight valence electrons.
• D. It does not change its electron configuration and remains neutral.

Answer: (B)

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 the electron configuration of a calcium atom: calcium has 20 electrons, with the valence shell configuration of 4s^2, meaning it has 2 electrons in its outermost shell.
3. Recognize that calcium is a metal and typically loses electrons rather than gaining them to achieve stability.
4. Determine that calcium loses its two valence electrons (the 4s^2 electrons) to form a Ca^{2+} ion, resulting in the electron configuration of the previous noble gas, argon, which has a full octet.
5. Conclude that by losing two electrons, calcium obeys the octet rule and attains a stable electron configuration similar to a noble gas.