Which of the following is NOT a valid Lewis dot structure based on the octet rule exceptions?

• A. BF3 with boron surrounded by 6 electrons
• B. BeCl2 with beryllium surrounded by 8 electrons
• C. SF6 with sulfur surrounded by 12 electrons
• D. NH3 with nitrogen surrounded by 8 electrons

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the octet rule and its exceptions. The octet rule states that atoms tend to have 8 electrons in their valence shell to achieve stability, but some elements can have fewer or more than 8 electrons due to their position in the periodic table or bonding characteristics.
2. Step 2: Analyze BF3. Boron is an exception to the octet rule and often forms stable compounds with only 6 valence electrons around it. Therefore, BF3 with boron surrounded by 6 electrons is a valid Lewis structure.
3. Step 3: Analyze SF6. Sulfur is in period 3 and can expand its octet by using d orbitals, allowing it to have 12 electrons around it. Thus, SF6 with sulfur surrounded by 12 electrons is a valid Lewis structure.
4. Step 4: Analyze NH3. Nitrogen typically follows the octet rule and forms three bonds plus one lone pair, totaling 8 electrons around it. NH3 with nitrogen surrounded by 8 electrons is a valid Lewis structure.
5. Step 5: Analyze BeCl2. Beryllium is an exception that usually forms compounds with only 4 electrons around it, not 8. Therefore, BeCl2 with beryllium surrounded by 8 electrons violates the octet rule and is NOT a valid Lewis structure.