Question

a.Which of the species have bond angles of 109.5°?

b. Which of the species have bond angles of 120°?

H₂O H₃O^{+ +}CH₃ BF₃ NH₃ ⁺NH₄ ^-CH₃

Short answer

1. H₂O, H₃O⁺, NH₃,⁺NH₄ have 109.5° bond angle.
2. ⁺CH₃, BF₃, ^-CH₃, have 120° bond angle.

Step-by-step solution

Bond angle

It is basically the angle between the central atom and the atoms attached to it.

In case of Sp³hybrid orbital, the bond angle is 109.5° and for sp² orbital, the bond angle is 120°.

Estimation of bond angle of the following molecules

The assign the bond angle, we first have to find the which is sp² and which is sp³ molecule.

So, first we have to calculate the hybridisation.

Hybridisation=No of atoms attached to central atom-1/2 (Valency of central atom (H))-Valency of attached atom(V)-Charge of Cation(C)+charge of Anion(X)

Bond angle ofH₂O :

Hybridisation=2+1/2(6-2)

Hybridisation= sp³

Bond angle ofH₃O⁺ :

Hybridisation=3+1/2(6-3-1)

Hybridisation= sp³

Bond angle of ⁺CH₃ :

Hybridisation=3+1/2(4-3-1)

Hybridisation= sp²

Bond angle of BF₃ :

Hybridisation=3+1/2(3-3)

Hybridisation= sp²

Bond angle of NH₃ :

Hybridisation=3+1/2(5-3)

Hybridisation= sp³

Bond angle of ⁺NH₄ :

Hybridisation=4+1/2(5-4-1)

Hybridisation= sp³

Bond angle of ^-CH₃ :

Hybridisation=3+1/2(4-3+1)

Hybridisation= sp².

1. H₂O, H₃O⁺, NH₃,⁺NH₄ have 109.5° bond angle.
2. ⁺CH₃, BF₃, ^-CH₃, have 120° bond angle.