from the lewis structures of the species given, pick all of those in which the central atom obeys the octet…
from the lewis structures of the species given, pick all of those in which the central atom obeys the octet rule. none of the above
Answer
Explanation:
Step1: Analyze first structure
In $AlCl_3$, Al has 6 valence - electrons around it (3 bonding pairs with Cl), so it does not obey the octet rule.
Step2: Analyze second structure
In $NOF$, N has 10 valence - electrons around it (4 bonding pairs and 1 lone pair), so it does not obey the octet rule.
Step3: Analyze third structure
In $I_3^-$, the central I atom has 10 valence - electrons around it (2 bonding pairs and 3 lone pairs), so it does not obey the octet rule.
Step4: Analyze fourth structure
In $CH_3^-$, C has 8 valence - electrons around it (3 bonding pairs with H and 1 lone pair), so it obeys the octet rule.
Answer:
The structure in which the central atom obeys the octet rule is the one with $CH_3^-$ (the fourth - given structure).