What is an inert pair? How can it affect chemical bonds between atoms of different groups (IUPAC)?

 An "inert pair" is a term used to describe the electrons in the outermost s-subshell of certain elements in the periodic table, such as the elements in Group 14 (carbon, silicon, germanium, tin, and lead) and Group 15 (nitrogen, phosphorus, arsenic, antimony, and bismuth) . These electrons are relatively shielded from the positively charged nucleus by the inner electrons, making them less likely to participate in chemical bonding.

This "inert pair" effect can affect chemical bonds between atoms of different groups in different ways. For example, in compounds containing the element silicon, the inert pair effect can make the silicon atom less likely to form double or triple bonds, which is why silicon compounds tend to have higher bond energies than expected. Similarly, in compounds containing the element phosphorus, the inert pair effect can make the phosphorus atom less likely to form five or six coordinate covalent compounds, which is why phosphorous compounds tend to have fewer coordination sites than expected.

In addition, the presence of an inert pair of electrons can affect the reactivity of the element and its compounds, making them more or less reactive than expected. For example, compounds containing elements with an inert pair of electrons are generally less reactive towards nucleophiles and electrophiles than their congeners without inert pair.

In summary, the inert pair effect refers to the behavior of certain electrons in the outermost s-subshell of certain elements in the periodic table, which can affect the chemical reactivity and bonding of those elements.