Question

Here, $B{{F}_{3}}$ is taken as an example of Lewis acid because it behaves:

Answer 1

Acids are those compounds which have a tendency to donate a proton i.e. hydrogen ion to any substance. Acids basically turn blue litmus paper to red and have a sour taste. The most common acid is citric acid present in lemon.

Complete answer:
Those compounds which have a high tendency to donate an electron pair always show high electron affinity. Those chemical species which have the ability to donate an electron pair to a given Lewis acid in order to form adducts are known as Lewis bases.
Electrophile is generally made up from two words called electro and phile where electro means electron and phile means loving i.e. those species that are electron loving in nature. Water generally contains one oxygen and two hydrogen atoms. It is inorganic, transparent, tasteless and colorless.
According to the Bronsted- Lewis concept an acid is defined as a substance which requires electrons and can accept lone pairs and behaves as an electrophile. Here we know that electronic configuration of boron is $1{{s}^{2}}2{{s}^{2}}2{{p}^{1}}$ $1{{s}^{2}}2{{s}^{2}}2{{p}^{1}}$ and here we see vacant p-orbital exist which indicates $B{{F}_{3}}$ has the tendency to accept lone pair so $B{{F}_{3}}$ is lewis acid and behaves as an electrophile.
So we can say that $B{{F}_{3}}$ is taken as an example of Lewis acid because it behaves as an electrophile.

Note:
Lewis bases are electron-rich species that we can say that they have the ability to donate electron-pairs and these are classified in the category of nucleophiles while Lewis acids are kept in the category of electrophiles.