Question

Of these molecules, which one is an electrophile and which one is a nucleophile?
$N{H_3},N{H_4}^ + ,{H^ + },O{H^ - },{H_2}O,$ and $BC{l_3}$

Answer 1

Molecules are formed by the combination of atoms. Molecules may lose or gain electrons to become ions. Molecules are classified into electrophiles and nucleophiles based on their nature. Electrophiles are the electron deficient or electron loving groups and nucleophiles are electron rich compounds.

Complete Step By Step Answer:
Electrophiles are electron deficient compounds or electron loving groups generally consisting of positive charge, but some electrophiles do not consist of any charge. These are attracted by electron rich species.
Ammonia is a molecule which is represented by the chemical formula of $N{H_3}$ , due to the presence of lone pairs of electrons, ammonia is a nucleophile.
Ammonium ion is an electrophile represented by $N{H_4}^ +$ , it is a conjugate acid of ammonia and readily attracts towards an electron rich compound. Thus, it is an electrophile.
Proton is an electrophile represented by ${H^ + }$ , it is an electron deficient compound and attracts towards an electron rich compound. Thus, it is an electrophile.
Hydroxide ion is a nucleophile represented by $O{H^ - }$ , it has a negative charge and can attract electron deficient compounds and is itself considered as a nucleophile.
Water can act as both electrophile and nucleophile, due to the presence of lone pairs of electrons, it can act as a nucleophile, but water can release ${H^ + }$ and has electrophilic character.
Boron trichloride is represented by a molecular formula of $BC{l_3}$ ; due to the presence of vacant p-orbital, it acts as an electrophile.

Note:
Due to the polarity of atoms in oxygen, it can act as a nucleophile. Water can release a proton ${H^ + }$ which is known as Lewis acid as an acid release ${H^ + }$ and considered as an electrophile. Whereas boron trichloride does not carry any charge, but due to the empty $2{p_z}$ orbital perpendicular to the plane accepting electrons makes it an electrophile.