Question

the covalent radius increases from nitrogen to Bi. but the increase in the radius from As to Bi is very small. this is due to

Answer 1

The increase in covalent radius is due to completely filled d and f orbital.

• Both As (Arsenic) and Bi (Bismuth) belong to the periodic table at group 15.
• The size of the atom decreases as a new shell of electrons is introduced and the electrons lie farther away from the nucleus.
• However as there is a shift from As to Bi, due to the presence of fully filled d and f orbitals only a slight increase in size is observed.The d and f orbitals are diffused due to which the electrons present in those orbitals do not effectively screen the nuclear charge.
• The valence electrons are thus drawn to the nucleus more strongly and are pushed closer to the nucleus because of weak shielding effect of internal d and f electrons. Hence the increase in As to Bi size is small.