Question

Superoxides of alkali metals act as oxidising agents while normal oxides are basic in nature. The oxide which is paramagnetic in nature due to presence of unpaired electron is (a) \(\mathrm{Na}_{2} \mathrm{O}_{2}\) (b) \(\mathrm{KO}_{2}\) (c) \(\mathrm{Na}_{2} \mathrm{O}\) (d) \(\mathrm{K}_{2} \mathrm{O}_{2}\)

Short answer

\(\mathrm{KO}_{2}\) is the compound that is paramagnetic due to the presence of an unpaired electron.

Step-by-step solution

- Understand superoxide compounds

Superoxides are compounds of the alkali metals where the metal is bound to the superoxide ion (O2-). This ion has an odd number of electrons, which means that there will be at least one unpaired electron, leading to paramagnetism. Normal oxides, on the other hand, have oxide ions (O2-) with paired electrons and are usually basic with no magnetic properties.

- Identify the superoxide

From the given options, we need to look for a superoxide compound, which implies that we are looking for a chemical formula that includes the superoxide ion O2-. The correct superoxide will have this ion, indicating the presence of an unpaired electron.

- Determine the paramagnetic compound

\(\mathrm{Na}_{2}\mathrm{O}_{2}\) and \(\mathrm{K}_{2}\mathrm{O}_{4}\) are both normal oxides and do not contain the superoxide ion. \(\mathrm{Na}_{2}\mathrm{O}\) is also a normal oxide. Only \(\mathrm{KO}_{2}\) contains the superoxide ion (O2-) making it the compound that is paramagnetic in nature due to the presence of an unpaired electron.

Key concepts

Paramagnetism in Chemistry

Paramagnetism is a form of magnetism which occurs due to the presence of unpaired electrons in the atomic or molecular structure of materials. In the context of superoxides of alkali metals, like \( \mathrm{KO}_{2} \), the paramagnetic property arises because of the superoxide ion (\(O_2^-\)), which has an unpaired electron in its molecular orbital.

Due to this unpaired electron, paramagnetic substances are attracted by an external magnetic field. The strength of the magnetism is directly proportional to the number of unpaired electrons. Therefore, superoxides, which contain an odd number of electrons, exhibit paramagnetism, and this unique feature allows such materials to be distinguished from other compounds, like normal oxides, which are usually diamagnetic or weakly paramagnetic because all their electrons are paired.

Oxidising Agents

Oxidising agents are substances that can accept electrons in a chemical reaction. This concept is critical when studying superoxides of alkali metals, as these compounds are strong oxidising agents. The superoxide ion, with its odd electron, has a strong tendency to gain an electron to achieve a more stable electronic arrangement.

This makes alkali metal superoxides, such as \( \mathrm{KO}_{2} \), highly reactive toward substances that can donate electrons. In the process of oxidation, the superoxide ion is reduced by gaining an electron, while the electron donor is oxidised. This distinguishing capability of superoxides is leveraged in various applications, like in oxygen generation systems, where they act as sources of oxygen by releasing it through a reaction with carbon dioxide.

Basic Oxides

Basic oxides are typically formed by the reaction of oxygen with metals, especially the alkali metals. These oxides react with water to form alkaline hydroxides, which are characterized by their ability to neutralize acids. This is in contrast to acidic oxides, which react with bases to form salts and water.

Normal oxides of alkali metals tend to be basic, such as \( \mathrm{Na}_{2}\mathrm{O} \) and \( \mathrm{K}_{2}\mathrm{O} \). They are made up of oxide ions (\(O^{2-}\)), where all electrons are paired and thus do not display paramagnetism. Alkali metal oxides are also known for their high reactivity with water to form corrosive alkaline solutions, an attribute that industries might harness in applications like deacidifying environments and as catalysts in chemical syntheses.