Which of the following neutral compounds has a central atom with a complete octet based on its Lewis dot diagram?

• A. BeCl2
• B. CO2
• C. NO2
• D. BF3

Answer: (B)

Verified step by step guidance

1. Identify the central atom in each molecule and determine its valence electrons. For example, in BeCl2, Be is the central atom; in CO2, C is central; in NO2, N is central; and in BF3, B is central.
2. Draw the Lewis dot structure for each molecule by arranging the valence electrons around the atoms, forming bonds between the central atom and surrounding atoms, and distributing remaining electrons as lone pairs to satisfy the octet rule where possible.
3. Count the total number of electrons around the central atom in each Lewis structure, including bonding and lone pair electrons. Remember that each bond counts as two electrons.
4. Check if the central atom has a complete octet, meaning it is surrounded by 8 electrons. Note that some atoms like Be and B often have fewer than 8 electrons and are exceptions to the octet rule.
5. Compare the structures: Be in BeCl2 typically has only 4 electrons, B in BF3 has 6 electrons, N in NO2 often has an odd number of electrons (an odd-electron species), while C in CO2 has a full octet with double bonds to oxygen atoms.