KCET 2026 Chemistry Solved Paper

Concept:Higher oxidation states are stabilised by the ability to form multiple bonds; oxygen can do this, while fluorine cannot.Explanation:In $\mathrm{MnF}_4$, fluorine has oxidation state $-1$.If the oxidation state of Mn is $x$, then:$$x + 4(-1) = 0 \Rightarrow x = +4$$So manganese shows only $+4$ with fluorine.In $\mathrm{Mn}_2\mathrm{O}_7$, oxygen has oxidation state $-2$.Let the oxidation state of Mn be $x$:$$2x + 7(-2) = 0 \Rightarrow 2x - 14 = 0 \Rightarrow x = +7$$So manganese shows $+7$ with oxygen.Fluorine is highly electronegative, but it can form only one single bond because it needs only one electron to complete its octet.It cannot form multiple bonds with manganese, so it cannot stabilise very high oxidation states like $+7$.Oxygen can form double bonds with metals, and these multiple bonds help stabilise higher oxidation states.Therefore, the correct reason is that in covalent compounds, fluorine can form a single bond only, while oxygen forms a double bond.Answer:Option D: In covalent compounds, fluorine can form single bond only, while oxygen forms double bond.