Question

Account for the following: The experimentally determined N-F bond length in $NF_{3}$ is greater than the sum of the single covalent radii of N and F.

Answer 1

Observing the periodic table Nitrogen is the element belong to the group 15 which was also called pnictogens. Fluroine is the element belong to the group 7 which was also called halogens.

The reason that the length of the bond of N-F in the element NF3 seems to be greater than the total sum of the single covalent radii of N and F because Nitrogen and Fluroine are small and have highest electro density hence they do not attract each other and the pair of electrons which was bonded leading to the larger size of the bond than expected.