Why the stability of $+6$ the oxidation state in a group $16$ decreases down the group and $+4$ increases down the group?

Oxidation States:

• The oxidation state of an atom (also called the oxidation number) in a chemical compound takes into consideration the range of electrons lost and as a result displays the extent of oxidation of the atom.
• An atom's oxidation state is described because the theoretical charge an atom could have if all of its hyperlinks to different atoms had been absolutely ionic in nature.

Reason for decreasing stability of 6 oxidation state in group $16$ down the group.

• Elements in Group $16$ have ${\mathrm{ns}}^2{\mathrm{np}}^4$ arrangement
• As a result, they ought to have a most oxidation number of $+6$ , but the heavier atoms have a decrease oxidation nation, i.e., $+4$ .
• This is due to the inert pair effect, which reasons s-electrons to stay coupled and now no longer take part in bond formation.
• Because the s-orbitals are near the nucleus, the electrons withinside the s-orbitals are tightly held bye nucleus because of the great electrostatic force.
• The electrons stay coupled due to the fact the power required to unpair those s-electrons is considerable.
• As a result, the steadiness of the $+6$ oxidation state falls at the same time as the steadiness of the $+4$ oxidation state improves as one movements down the group.