Choose the incorrect statement from the following

(1) Correct: $Cu^+$ is unstable in aqueous medium due to the much higher hydration energy of $Cu^{2+}$. It undergoes disproportionation: $2Cu^+(aq) \to Cu^{2+}(aq) + Cu(s)$.

(2) Correct: Oxidising power decreases down Group 6. $CrO_3$ is a strong oxidant while $MoO_3$ and $WO_3$ are much weaker.

(3) Incorrect: Oxygen can stabilise higher oxidation states through multiple bonding (e.g., in oxoanions like $MnO_4^-$, $CrO_4^{2-}$). The ability of oxygen to stabilise higher oxidation states is superior to that of fluorine in many cases. So the statement that fluorine exceeds oxygen is incorrect.

(4) Correct: $Cr^{2+}(d^4)$ is oxidised to $Cr^{3+}(d^3$, stable $t_{2g}^3)$. $E°(Cr^{3+}/Cr^{2+}) = -0.41$ V, while $E°(Fe^{3+}/Fe^{2+}) = +0.77$ V. Lower reduction potential means $Cr^{2+}$ is a stronger reducing agent than $Fe^{2+}$.

The incorrect statement is (3).