Problem 93 - A Complete Resource Book in Chemistry for JEE Main

Question

Which among the following is paramagnetic? (a) \(\mathrm{ClO}_{2}\) (b) \(\mathrm{Cl}_{2} \mathrm{O}_{6}\) (c) \(\mathrm{Cl}_{2} \mathrm{O}\) (d) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\)

Step-by-Step Solution

Answer

\( \mathrm{ClO}_2 \) is paramagnetic because it has unpaired electrons.

Step 1: Understanding Paramagnetism

Paramagnetism occurs when a molecule has one or more unpaired electrons. Check the electronic configuration of each given molecule to identify any unpaired electrons.

Step 2: Analyze Molecule (a)

Consider the molecule \( \mathrm{ClO}_2 \). This molecule has an odd number of total electrons, resulting in at least one unpaired electron. \( \mathrm{ClO}_2 \) has typically one unpaired electron, making it paramagnetic.

Step 3: Analyze Molecule (b)

For \( \mathrm{Cl}_2\mathrm{O}_6 \), calculate the electron distribution. This molecule does not have unpaired electrons in its valence shell as all bonds are fulfilled leading to no paramagnetic behavior.

Step 4: Analyze Molecule (c)

Examine \( \mathrm{Cl}_2 \mathrm{O} \). This molecule usually has all electrons paired, contributing no unpaired electrons and hence not showing paramagnetism.

Step 5: Analyze Molecule (d)

Look at \( \mathrm{Cl}_2 \mathrm{O}_7 \). A stable electronic structure in \( \mathrm{Cl}_2 \mathrm{O}_7 \) without unpaired electrons means it is diamagnetic rather than paramagnetic.

Step 6: Conclusion

Based on the analysis, only \( \mathrm{ClO}_2 \) exhibits paramagnetism due to the presence of unpaired electrons. None of the other options show this property.

Key Concepts

Unpaired Electrons

Unpaired electrons play a crucial role in determining whether a substance exhibits paramagnetism or diamagnetism. Electrons are negatively charged particles that usually pair up within atomic or molecular orbitals. When electrons are paired, their opposite spins cancel each other out, and the molecule does not exhibit a net magnetic moment. However, when there are unpaired electrons, as in the case of certain radicals and transition metals, this results in a net spin. The presence of these unpaired electrons is what gives rise to paramagnetic behavior. Paramagnetic substances are attracted to magnetic fields due to their unpaired electrons. In our example, the molecule - \( ClO_2 \) exhibits paramagnetism because it has an unpaired electron. This sets it apart from other molecules like \( Cl_2O_6 \) or \( Cl_2O_7 \), where all electrons are paired, resulting in a lack of magnetic properties. Understanding the presence of unpaired electrons helps identify the magnetic characteristics of a material.

Electronic Configuration

Electronic configuration is a systematic way of distributing electrons among the orbitals of atoms in a molecule. It's critical for understanding magnetism and other chemical properties. Each molecule has a unique electronic configuration, which helps us predict whether it is paramagnetic or diamagnetic. For instance, consider the molecule \(ClO_2\). Its total number of electrons is an odd number, inherently suggesting the presence of one or more unpaired electrons. On the other hand, molecules like \(Cl_2O_6\) possess an even number of electrons, implying that all electron slots could be fully paired, effectively leading to a stable and diamagnetic nature. Understanding electronic configurations allows chemists to visualize the electron distribution across molecular orbitals. This understanding becomes especially important in predicting how a molecule might behave in a magnetic field.

Molecular Analysis

Molecular analysis dives deeper into understanding the structure and behavior of molecules, including their magnetic properties. This analysis involves examining the distribution and pairing of electrons within molecules to predict whether they exhibit paramagnetism or diamagnetism. - In our exercise, \( ClO_2 \) was determined to be paramagnetic through molecular analysis, as it contained an unpaired electron in its valence shell. - For molecules like \( Cl_2O_6 \) and \( Cl_2O_7 \), more advanced analysis involves looking at their stable structures, where the electron distribution leads to a fully paired electron system, verifying their diamagnetic behavior. By engaging in molecular analyses, scientists and students alike understand which molecular characteristics lead to distinct magnetic behaviors, allowing them to predict and explain the properties of unknown compounds.

Diamagnetism

Diamagnetism is a form of magnetism where substances are repelled by magnetic fields. This phenomenon occurs due to the absence of unpaired electrons. When all electrons in an atom or molecule are paired, their magnetic moments perfectly cancel each other out, giving a net magnetic moment of zero. Molecules such as \(Cl_2O_6\) and \(Cl_2O_7\) are examples of diamagnetic substances because they have fully paired electrons. The electrons in these molecules do not contribute to the net magnetism, thus showing negligible interaction with external magnetic fields. This is in stark contrast to paramagnetic molecules like \(ClO_2\), which have unpaired electrons resulting in attraction to magnetic fields. Understanding diamagnetism is important in fields like magnetic levitation and MRI technology, where molecules' interactions with magnetic fields can be put to practical use.