Question

What is the effect of lone pair on bond length?

Answer 1

Lone Pairs of electrons on neighboring atoms weaken the bond because of electron repulsion. Neighboring atoms in a molecule that have lone pair electrons will not be held together in their bond as tightly because the lone pair electrons of both atoms repel each another. That is part of the reason why, for example, the bond in an H2 molecule is so strong - because there are no lone pair electrons on the hydrogen atoms to repel one another