Match List-I (observation about the higher oxidation states of 3d metals) with List-II (reason).
| List-I | List-II |
|---|---|
| (A) Fluorine stabilises the +3 state of cobalt in CoF3 | (I) Ability to form multiple bonds to the metal |
| (B) Fluorine stabilises the +6 state of chromium in CrF6 | (II) Hydrolysis of the other halides to give oxohalides |
| (C) The highest oxide of manganese, Mn2O7, has a higher oxidation state of the metal than its highest fluoride, MnF4 | (III) Higher lattice energy |
| (D) Among the halides, the +5 state of vanadium is represented only by VF5 | (IV) Higher bond enthalpy terms for the higher covalent compounds |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A-III, B-IV, C-I, D-II
The highest oxidation states of the 3d metals are found in their fluorides and oxides, because fluorine and oxygen can stabilise high oxidation states. The reason differs from compound to compound.
(A) Fluorine stabilises the +3 state of cobalt in CoF3 — This matches (III) Higher lattice energy. The high lattice energy of CoF3 makes the +3 state of cobalt stable in this fluoride.
(B) Fluorine stabilises the +6 state of chromium in CrF6 — This matches (IV) Higher bond enthalpy terms for the higher covalent compounds. CrF6, like VF5, is a covalent fluoride; its strong bonds make the high state stable.
(C) The highest oxide of manganese, Mn2O7, has a higher oxidation state of the metal than its highest fluoride, MnF4 — This matches (I) Ability to form multiple bonds to the metal. Mn is +7 in Mn2O7 but only +4 in MnF4; oxygen can form multiple bonds, so it stabilises high states better than fluorine.
(D) Among the halides, the +5 state of vanadium is represented only by VF5 — This matches (II) Hydrolysis of the other halides to give oxohalides. The other vanadium(V) halides undergo hydrolysis and appear as the oxohalides VOX3 instead.
NCERT (2026-27 edition):
4.3.7 Trends in Stability of Higher Oxidation States – “…The ability of fluorine to stabilise the highest oxidation state is due to either higher lattice energy as in the case of CoF3, or higher bond enthalpy terms for the higher covalent compounds, e.g., VF5 and CrF6. Although V+5 is represented only by VF5, the other halides, however, undergo hydrolysis to give oxohalides, VOX3.”
“…The ability of oxygen to stabilise these high oxidation states exceeds that of fluorine. Thus the highest Mn fluoride is MnF4 whereas the highest oxide is Mn2O7. The ability of oxygen to form multiple bonds to metals explains its superiority.”