Answer to Question #184666 in Molecular Physics | Thermodynamics for Jade

Question

1. Ammonia is polar molecule while boron trifluoride is a non polar molecule. Explain the difference in the polarity of these co pounds.

2. Suppose that AB3E a hypothetical moleculeis discovered . Predict whether the molecule is polar or nonpolar by determining its molecular shape.

Note : A- corresponds to central atom

B- Terminal atom

E-lone pair ( nonbonding electrons)

Answer 1

Answer:-

(1)

NH₃ has lone pair present on nitrogen atom

and

we know that nitrogen is more electronegative than hydrogen that causes electron movement in only one direction

and

It's dipole moment is greater than 0 , this implies NH₃ is polar molecule

BF₃ is non polar because dipole moment is 0,

Fluorine is more electronegative than boron that causes a electron movement from boron to fluorine and net movement = 0

(2)

AB₃E₁ =  A- corresponds to central atom

B- Terminal atom

E-lone pair

molecule is bent shape

as we can see in the diagram

$\bigstar$ It is a polar molecule

The bond angles are decreased below 109.5° because the lone pair has a slightly greater repulsive effect than the electrons in the covalent bonds between A and B.