Giving justification,categorise the following molecules/ions as nucleophile or electrophile: $HS^{-}, BF_{3}, C_{2}H_{5}O^{-}, (CH_{3})_{3}N:, \overset{+}{Cl}, CH_{3}-\overset{+}{C}=O, H_{2}N:^{-}, \overset{+}{N}O_{2}$

(N/A) Nucleophiles are electron-rich species that can donate an electron pair. These include: $HS^{-}, C_{2}H_{5}O^{-}, (CH_{3})_{3}N:, H_{2}N:^{-}$. These species possess at least one lone pair of electrons available for donation to an electrophile.
Electrophiles are electron-deficient species that can accept an electron pair. These include: $BF_{3}, \overset{+}{Cl}, CH_{3}-\overset{+}{C}=O, \overset{+}{N}O_{2}$. These species either have an incomplete octet (like $BF_{3}$) or a positive charge/reactive site that can accept an electron pair from a nucleophile.