Final answer:
Nucleophiles add close to the leaving group in an SN2 reaction.
Step-by-step explanation:
The incoming nucleophile approaches the electrophilic carbon from the side opposite to the leaving group. The nucleophile starts making the bond while the leaving group starts breaking the bond simultaneously. The other groups pointing away from the leaving group move to the other side, away from the incoming nucleophile. This reaction mechanism is called SN2 where S is for substitution, N is for nucleophilic, and 2 is for bimolecular.