Match List-I with List-II:

Choose the correct answer from the options given below:

(A) - (IV), (B) - (III), (C) - (I), (D) - (II)

The correct answer is Option (3) → (A) - (IV), (B) - (III), (C) - (I), (D) - (II).

Let us go through the items in List-I and List-II to explain the correct matches:

(A) Mn²⁺: (IV) Highest oxidation states

Manganese (Mn) is known for showing a wide range of oxidation states, from +2 to +7. Mn²⁺ is a common oxidation state, but manganese is notable for achieving its highest oxidation state (+7), such as in permanganate ions \((MnO_4^-)\). Therefore, Mn is associated with high oxidation states, which makes (A) - (IV) a correct match.

(B) Spin-only Magnetic Moment: (III) $μ_s=\sqrt{n(n+2)} BM$

The spin-only magnetic moment is a way to calculate the magnetic moment of a metal ion based on the number of unpaired electrons it has. The formula is \(\mu_s = \sqrt{n(n+2)}\) Bohr magnetons (BM), where \(n\) is the number of unpaired electrons. This formula is specific to the spin contribution to the magnetic moment and is used frequently for transition metal ions.

(C) MnO₂: (I) Pyrolusite ore

Manganese dioxide (MnO₂) occurs naturally as the mineral pyrolusite, which is the principal ore for manganese. Pyrolusite is important for extracting manganese and is used in various industrial processes.

(D) Mischmetal: (II) An alloy of 4f metal, iron and traces of S, C, Al and Ca

Mischmetal is an alloy that consists primarily of rare earth elements (which are 4f metals like cerium, lanthanum, and neodymium), along with iron and small amounts of sulfur, carbon, aluminum, and calcium. Misch metal is used in flints for lighters and other applications.

Hence, the correct answer is: (A) - (IV), (B) - (III), (C) - (I), (D) - (II).