Question

The molecule $B{F}_3$ and $N{F}_3$, both are covalent compounds but $B{F}_3$ is non-polar and $N{F}_3$ is polar. The reason is that:

• A. boron is a metal and nitrogen is a gas in uncombined state
• B. $B{F}_3$ bonds have no dipole moment whereas $N{F}_3$ bond have dipole moment
• C. atomic size of boron is smaller than that of nitrogen
• D. $B{F}_3$ is symmetrical molecule whereas $N{F}_3$ is unsymmetrical

Answer 1

Answer: (D)

$B{F}_3$ is symmetrical molecule whereas $N{F}_3$ is unsymmetrical

The molecule $B{F}_3$ and $N{F}_3$, both are covalent compounds but $B{F}_3$ is non-polar and $N{F}_3$ is polar. The reason is that $B{F}_3$ is symmetrical molecule whereas $N{F}_3$ is unsymmetrical.
In symmetrical molecule, the individual bond dipoles cancel each other whereas in unsymmetrical molecules, they do not.
$B{F}_3$ is plane triangular molecule whereas $N{F}_3$ has pyramidal geometry.