Which of the following statements are true?

(i) Mn has highest oxidation state in Mn₂O₇

(ii) MnO is more ionic than Mn₂O₇

(iii) Mn₂O₇ has one bridging O atom

(iv) Oxidation state of Mn is maximum in oxo compounds

Correct Answer: Only (i), (ii), (iii) and (iv) are correct

Let us analyze each statement step-by-step to understand the chemical principles involved:

Statement (i): Mn has highest oxidation state in Mn₂O₇

Let the oxidation state of Manganese (Mn) be x. Oxygen generally exhibits an oxidation state of -2 in oxides.

Setting up the oxidation number equation for Mn₂O₇:

$2x+7(-2)=0$

$2x-14=0$

$2x=14$

$x=+7$

Since Manganese belongs to Group 7 of the periodic table (valence shell configuration 3d⁵4s²), its maximum possible oxidation state is +7. Thus, Mn has its highest oxidation state (+7) in Mn₂O₇. Statement (i) is true.

Statement (ii): MnO is more ionic than Mn₂O₇

According to Fajan's Rules, as the oxidation state (positive charge) of a metal cation increases, its polarizing power increases, leading to greater covalent character in the bond. In MnO, Mn is in the lower oxidation state (+2), so it forms ionic bonds with basic character. In Mn₂O₇, Mn is in a very high oxidation state (+7), giving it high covalent character (it exists as a green covalent oil). Therefore, MnO is significantly more ionic than Mn₂O₇. Statement (ii) is true.

Statement (iii): Mn₂O₇ has one bridging O atom

The chemical structure of dimanganese heptoxide (Mn₂O₇) consists of two tetrahedral MnO₄ units sharing a single corner oxygen atom. Its bonding connectivity is represented as O₃Mn–O–MnO₃, featuring one central bridging Mn–O–Mn oxygen atom. Statement (iii) is true.

Statement (iv): Oxidation state of Mn is maximum in oxo compounds

Transition elements like Manganese display their highest oxidation states when bonded to small, highly electronegative atoms like Oxygen and Fluorine. However, Oxygen is capable of forming multiple bonds (pi-bonds) using its p-orbitals to stabilize high oxidation states better than Fluorine. Hence, Manganese exhibits its maximum oxidation state (+7) specifically in oxo compounds and oxoanions such as Mn₂O₇ and permanganate ion (MnO₄^-). Statement (iv) is true.

Since statements (i), (ii), (iii), and (iv) are all true, the correct option is Only (i), (ii), (iii) and (iv) are correct.