Question

For Lewis acids and bases, the base is defined as an electron pair donor / acceptor (circle the correct answer).

Answer 1

Answer: electron donor.

Explanation:

According to Arrhenius concept, a base is defined as a substance which donates hydroxide ions $(OH^-)$ when dissolved in water and an acid is defined as a substance which donates hydronium ions $(H_3O^+)$ in water.

According to the Bronsted Lowry conjugate acid-base theory, an acid is defined as a substance which donates protons and a base is defined as a substance which accepts protons.

According to the Lewis concept, an acid is defined as a substance that accepts electron pairs and base is defined as a substance which donates electron pairs.

$NH_3+H^+\rightarrow NH_4^+$

Here $NH_3$ acts as lewis base and $H^+$act as lewis acid.

Thus lewis base is defined as an electron pair donor.