Questions: From the Lewis structures of the species given, pick all of those in which the central atom obeys the octet rule.

Solution Steps

The central carbon atom in CH₄ has four single bonds, resulting in 8 valence electrons. It obeys the octet rule.

The central nitrogen atom in NO₃⁻ has a double bond and two single bonds and no lone pairs, giving it a total of 8 valence electrons. It obeys the octet rule.

The central phosphorus atom in PCl₅ has five single bonds, totaling 10 valence electrons. This exceeds the octet rule.

The central beryllium atom in BeF₂ has two single bonds, totaling 4 valence electrons. This is less than the octet, so it does not obey the octet rule.

Final Answer: The first two Lewis structures, CH₄ and NO₃⁻, obey the octet rule.