Question

Among the following, the paramagnetic compound is (A) \(\mathrm{Na}_{2} \mathrm{O}_{2}\) (B) \(\mathrm{O}_{3}\) (C) \(\mathrm{N}_{2} \mathrm{O}\) (D) \(\mathrm{KO}_{2}\)

Short answer

The paramagnetic compound is (D) \(\mathrm{KO}_{2}\).

Step-by-step solution

Understand Paramagnetism

Paramagnetic substances are those that have unpaired electrons and are attracted by a magnetic field. The presence of unpaired electrons can be determined by the electronic configuration of the compound's constituent atoms and their bonding.

Analyze Option (A) - \(\mathrm{Na}_{2} \mathrm{O}_{2}\)

Sodium superoxide (\(\mathrm{Na}_{2} \mathrm{O}_{2}\)) consists of \(\mathrm{Na}^+\) ions and \(\mathrm{O}_2^{2-}\) ions. \(\mathrm{O}_2\) in \(\mathrm{O}_2^{2-}\) has all electrons paired, thus it is not paramagnetic.

Analyze Option (B) - \(\mathrm{O}_{3}\)

Ozone (\(\mathrm{O}_{3}\)) has a resonating structure with all electrons paired. Hence, it is not paramagnetic.

Analyze Option (C) - \(\mathrm{N}_{2} \mathrm{O}\)

Nitrous oxide (\(\mathrm{N}_{2} \mathrm{O}\)) has a linear structure with all electrons paired. Therefore, it is not paramagnetic.

Analyze Option (D) - \(\mathrm{KO}_{2}\)

Potassium superoxide (\(\mathrm{KO}_{2}\)) consists of \(\mathrm{K}^+\) ions and \(\mathrm{O}_2^-\) ions. The \(\mathrm{O}_2^-\) ion, known as a superoxide ion, has an odd number of electrons resulting in at least one unpaired electron, which makes it paramagnetic.

Key concepts

Paramagnetism

Paramagnetism is a form of magnetism that occurs in materials with at least one unpaired electron. Unlike diamagnetic substances, which are repelled by magnetic fields, paramagnetic materials are attracted to magnetic fields regardless of how weak the field may be.
This attraction is due to the magnetic moments of the unpaired electrons, which, although typically randomly oriented, align in the direction of an external magnetic field, causing the material to be drawn into the field. The strength of a material's paramagnetic properties can be determined by the number of unpaired electrons present.

Real-World Examples

Everyday examples of paramagnetic substances include aluminum, oxygen (under specific conditions), and certain transition metal complexes. These materials can often be identified in a laboratory setting using a simple magnet. It's important to note that paramagnetic attraction is weaker compared to the strong magnetic attraction observed in ferromagnetic materials, which have permanently aligned magnetic moments.

Electronic Configuration

The electronic configuration of an atom or molecule describes the distribution of electrons in atomic or molecular orbitals. Each element has a unique arrangement of electrons that can be predicted using the principles of quantum mechanics and follows a specific order, often denoted by the Aufbau principle, Hund's rule, and the Pauli exclusion principle.
An atom's ground state configuration reflects its most stable arrangement of electrons, and can be depicted using notation that includes the quantum numbers or electron configuration diagrams. Understanding the electronic configuration is crucial as it dictates an element's chemical behavior, its interactions with other atoms, and its magnetic properties.

The Significance in Magnetism

In the context of paramagnetism, the electronic configuration is used to determine whether an atom or compound has unpaired electrons, which is necessary for a substance to be considered paramagnetic.

Unpaired Electrons

Unpaired electrons are those that do not have an opposite electron with the same energy level in a paired state. An electron is considered paired when two electrons occupy the same orbital but have opposite spins, as dictated by the Pauli exclusion principle. Atoms or molecules with unpaired electrons have incomplete electron shells or subshells, making them susceptible to magnetic fields.
When subjected to a magnetic field, these unpaired electrons can align with the field, giving rise to magnetic properties within the material. The presence of unpaired electrons is a key factor in determining whether a substance is paramagnetic or not.

Identifying Unpaired Electrons

The simplest way to identify whether electrons are paired or unpaired in an atom or molecule is to write out its electron configuration or electron box diagram and examine the arrangement of the electrons. These unpaired electrons are pivotal not only in magnetism but also play a significant role in the chemical reactivity and color of compounds.