Question

Identify the following as Lewis acids or bases. For a polyatomic molecule, you should be concerned with the central atom, e.g., the nitrogen in NH3

b. Co2+

d. N(CH3)3

e. BBr3

f. AlCl3

g. K+

h. Ca2+

i. Hg2 2+

Answer 1

A Lewis acid is the one which is having less number of electrons than that of an octet.

A Lewis base is the one which is having more number of electrons than that of an octet.

(b)The electronic configuration of Co²⁺ is [Ar] 4s⁰ 3d⁷

So in the outer most shell there is only 7 electrons (less number of electrons than that of an octet) so it acts as Lewis acid.

(d) In N(CH₃)₃ ( N belongs to 15th group, having 5 valency electrons), there are three bond pairs & one lone pair of electrons, so there is excess number of electrons on N so it acts as Lewis base.

(e) In BBr₃ ( B belongs to 13th group, having 3 valency electrons), there are only three bond pairs & no lone pair of electrons,so B having less number of electrons than that of an octet so it acts as Lewis acid.

(f) In AlCl₃ ( Al belongs to 13th group, having 3 valency electrons), there are only three bond pairs & no lone pair of electrons,so Al having less number of electrons than that of an octet so it acts as Lewis acid.

(g) The electronic configuration of K⁺ is [Ar] 4s⁰

So in the outer most shell there are no valency electons,so K⁺ neither acts as Lewis acid nor Lewis base.

(h) The electronic configuration of Ca²⁺ is [Ar] 4s⁰

So in the outer most shell there are no valency electons,so Ca²⁺ neither acts as Lewis acid nor Lewis base.

(i) The electronic configuration of Hg⁺ is [Xe] 4f¹⁴ 5d¹⁰ 6s¹
So in the outer most shell there is only one valency electon,so Hg₂²⁺ acts as Lewis base.