Question

Name the term used for a reagent that brings an electron pair.

Answer 1

Hint : A reagent which can “bring” an electron pair should be possessing an extra electron pair in the first place. Any species having an extra electron pair can donate it to electron-seeking species. They can thus form covalent bonds.

Complete Step By Step Answer:
The term used for a reagent that brings an electron pair is Nucleophile. A nucleophile is a reactant that possesses a pair of electrons. This pair of electrons is readily available for donation to another reactant which seeks an electron pair. Such a reactant which seeks a pair of electrons is called an electrophile. An electrophile can be considered as an “electron loving” species, while a nucleophile can be considered as an “electron-hating'' species. When a nucleophile donates an electron, it gains a positive charge, while the electron accepting electrophile gains a negative charge.
Nucleophiles can also be put forward as a species which has a surplus of electrons, or is electron-rich. It donates electrons to electron-deficient species. Electrophiles on the other hand are electron-deficient species, seeking electrons from electron-rich species. Nucleophiles can be identified by their strong attraction towards positive nuclei. Any molecule or atom carrying a negative charge is a nucleophile, as it has a lone pair of electrons which it can lose or donate. Nucleophiles are Lewis bases because of their ability to donate electrons.

Note :
Nucleophiles take part in nucleophilic substitution reactions. Nucleophilic substitution reactions are organic reactions where one nucleophile exchanges or substitutes another nucleophile in an organic compound. Some examples of nucleophiles are halogen ions $\left( {C{l^ - },{\text{ }}B{r^ - }} \right)$ , ammonia $\left( {N{H_3}} \right)$ , hydroxide ion $\left( {O{H^ - }} \right)$ et cetera.