Which of the following compounds is most likely to have an atom with an incomplete octet?

• A. CH4
• B. NH3
• C. CO2
• D. BF3

Answer: (D)

Verified step by step guidance

1. Recall the octet rule, which states that atoms tend to form bonds until they are surrounded by eight electrons in their valence shell, achieving a stable electron configuration similar to noble gases.
2. Examine each compound to determine if any atom has fewer than eight electrons around it after bonding: For CH4 (methane), carbon forms four single bonds, completing its octet.
3. For NH3 (ammonia), nitrogen forms three single bonds and has one lone pair, also completing its octet.
4. For CO2 (carbon dioxide), carbon forms two double bonds with oxygen atoms, satisfying the octet rule for carbon and oxygen.
5. For BF3 (boron trifluoride), boron forms three single bonds with fluorine atoms but only has six electrons around it, making it an example of an atom with an incomplete octet.