Answer
(a) Electron pairs being shared by atoms in a bond are called "bonding pairs" of electrons while any electron pairs remaining in the valence orbital of the central atom are called "lone pairs" of electrons.
(b) Lone pairs have a greater spatial requirement.
(c) Lone pair-lone pair repulsions > lone pair-bond pair repulsions > bond pair-bond pair repulsions
Work Step by Step
(a) Lone pairs are not involved in covalent bonding, unlike the bonding pairs of electrons. The electrons in a bonding pair usually come from one atom each. The lone pairs are called so since they stay with the atom, outside of the bonding activity, hence staying alone.
(b) Lone pairs are only bound to one nucleus at a time, so they spread more, and have a larger spatial arrangement compared to bonding pairs that are bound to two nuclei at the same time.
(c) Lone pairs repel each other the most since they're attached to the same nuclei and therefore are very close to each other. Relative to them, bonding electrons are shared by two different nuclei, so they have more distance and lesser repulsion.
