Question

hello.

a short summary (within 1 page) on 'relativistic effect in the context of inert pair effect.'

Answer 1

The inert pair effect is the reluctance of s-electrons to take part in bond formation. A chemical consequence is the occurrence of oxidation states which are two units less than the group oxidation.

Let us understand this in detail.

The electronic configuration of Group 13 elements is ns²np¹. Hence, they would be expected to be trivalent. However for the heavy elements lower oxidation states are more stable. This is explained by the s electrons remaining paired and not participating in bond formation. This inertness of s-subshell electrons towards the bond formation is called inert pair effect.

This happens because the s orbitals are held closer to the nucleus, therefore the electrons present in s orbitals are held strongly by nucleus because of large electrostatic forces. Hence the energy required to unpair the s-electrons is high because of which they remain paired.

For example:

1) In 13^th group, thallium can exhibit +1 and+3 oxidation states but it is stable in +1 oxidation state only due to inert pair effect

2) In 14^th group, lead shows both +2 and +4 oxidation states but it is stable in +2 oxidation state due to inert pair effect.

The inert-pair effect refers to the empirical observation that the heavier elements of groups 13–17 often have oxidation states that are lower by 2 than the maximum predicted for their group. For example, although an oxidation state of +3 is common for group 13 elements, the heaviest element in group 13, thallium (Tl), is more likely to form compounds in which it has a +1 oxidation state.

The inert pair effect says that the ns2 valence electrons of metallic elements, especially the 5s2 and 6s2 pairs that follow the second and third row of transition metals, are less reactive than would be expected based on periodic trends such as effective nuclear charge, atomic sizes, and ionization energies. In, Tl, Sn, Pb, Sb, Bi, and, To some extent, Po do not always show their expected maximum oxidation states. Rather, sometimes they form compounds in which their oxidation states are 2 less than what would be expected.