Match List - I with List - II:
List-I (Property)                  List-II (Example)
(a) Diamagnetism               (i) MnO
(b) Ferrimagnetism            (ii) O$$_2$$
(c) Paramagnetism            (iii) NaCl
(d) Antiferromagnetism     (iv) Fe$$_3$$O$$_4$$
Choose the most appropriate answer from the options given below:

We begin by recalling the basic magnetic behaviours shown by solids. A convenient way to predict the nature of magnetism is to look at the presence or absence of unpaired electrons and then note how the individual magnetic moments interact with one another in the crystal lattice.

Diamagnetism is the weakest form of magnetism. The defining feature is that every electron in the substance is paired, so the resultant magnetic moment of each ion, atom or molecule is zero. When an external magnetic field is applied, a very small negative magnetisation is induced (the substance is very slightly repelled). Typical examples are ionic salts made only of closed-shell ions such as $$\text{Na}^+$$ and $$\text{Cl}^-$$. Therefore $$\text{NaCl}$$ displays diamagnetism.

Paramagnetism appears when a species contains one or more unpaired electrons. Each unpaired electron possesses a magnetic moment, and in an external magnetic field these moments tend to align in the field direction, producing a weak attraction. The classic textbook example is the dioxygen molecule $$\text{O}_2$$, whose molecular-orbital diagram leaves two electrons unpaired in the degenerate $$\pi^*$$ orbitals. Hence $$\text{O}_2$$ is paramagnetic.

Ferrimagnetism occurs in solids where the magnetic moments are arranged on different lattice sites in antiparallel fashion but the magnitudes of the opposite moments are unequal, so a net magnetic moment survives. The best-known ferrimagnetic oxide is magnetite, $$\text{Fe}_3\text{O}_4$$, where $$\text{Fe}^{2+}$$ and $$\text{Fe}^{3+}$$ ions occupy different positions, producing incomplete cancellation of moments.

Antiferromagnetism is characterised by equal magnetic moments aligned antiparallel in such a way that they cancel each other completely, giving zero net magnetisation in the absence of a field. A simple binary oxide that shows this behaviour is manganese(II) oxide, $$\text{MnO}$$. Here the $$\text{Mn}^{2+}$$ ions (3d$$^5$$, five unpaired electrons) occupy lattice points so that half of them point “up” and half point “down”, resulting in exact cancellation.

Now we match each property from List-I with the correct example from List-II:

$$\begin{aligned} \text{(a) Diamagnetism} &\;\longrightarrow\; \text{NaCl } (iii)\\[2pt] \text{(b) Ferrimagnetism} &\;\longrightarrow\; \text{Fe}_3\text{O}_4 \; (iv)\\[2pt] \text{(c) Paramagnetism} &\;\longrightarrow\; \text{O}_2 \; (ii)\\[2pt] \text{(d) Antiferromagnetism} &\;\longrightarrow\; \text{MnO } (i) \end{aligned}$$

Looking at the given options, the sequence $$(a)-(iii),\; (b)-(iv),\; (c)-(ii),\; (d)-(i)$$ appears in Option D (labelled as Option 4).

Hence, the correct answer is Option D.