# Confusion regarding nucleophilicity [duplicate]

My teacher told me that to compare nucleophilicity, check the size of the attacking atom. Bigger the attacking atom more the nucleophilicity. But while reading Solomon, I found out that the order of nucleophilicity of halides in polar aprotic solvents is

$$\ce{F-}>\ce{Cl-}>\ce{Br-}>\ce{I-}$$

Which is opposite to the order expected from my teacher's explanation. How can we explain this order. Can I conclude that my teacher's explanation is valid only in protic solvents, and in aprotic solvents, more the basic strength implies more nucleophilicity, or this is just an exception?

• No. I read the answer before but was not satisfied. In Solomon it is written that this order is for aprotic solvents but the question says that order is different for different solvents, which is making me more confused Jun 20 at 9:39