Problem 113 - Chemistry The Molecular Nature of Matter

Question

Which of the following atoms in their ground states are expected to be paramagnetic: (a) \(\mathrm{Mn}\) (b) As, (c) S, (d) Sr, (e) \(\mathrm{Ar}\) ?

Step-by-Step Solution

Answer

Paramagnetic atoms from the list are: (a) \text{Mn} and (b) As. S, Sr, and Ar do not have unpaired electrons in their ground state configurations and are diamagnetic.

Step 1 - Determine the Electron Configuration

For each element, determine the ground state electron configuration to understand how the electrons are arranged in the atomic orbitals.

Step 2 - Identify Unpaired Electrons

Using the electron configurations, identify which atoms have unpaired electrons. An unpaired electron contributes to an atom's paramagnetism.

Step 3 - Determine Paramagnetism

Atoms with one or more unpaired electrons are paramagnetic. Analyze the electron configurations to determine which atoms meet this criterion.

Key Concepts

Electron Configuration

Understanding the electron configuration of an atom is fundamental in predicting its chemical and physical properties. The electron configuration describes how electrons are distributed among the various atomic orbitals in the ground state. Electrons fill orbitals starting from the lowest energy levels up to the higher ones, following the aufbau principle, Pauli exclusion principle, and Hund's rule. These guidelines ensure that the electrons occupy the available orbitals in a way that minimizes the energy of the atom.

The electron configuration is usually denoted by a series of numbers and letters that represent the principal quantum number, the type of orbital, and the number of electrons in those orbitals. For instance, hydrogen has an electron configuration of 1s¹, indicating one electron in the s orbital of the first energy level.

Unpaired Electrons

When examining the electron configurations of atoms to determine paramagnetism, one key aspect to look for is the presence of unpaired electrons. Unpaired electrons are those that do not have a corresponding electron with opposite spin in the same orbital. These lone electrons contribute to the magnetic properties of an atom.

Atoms that have one or more unpaired electrons exhibit paramagnetism, which means they are attracted to external magnetic fields due to their magnetic dipole moments. The more unpaired electrons an atom has, the stronger its paramagnetic properties will be. It is important to note that when an atom has all electrons paired, with spins canceling each other out, it is considered diamagnetic and will be slightly repelled by a magnetic field.

Ground State

The ground state of an atom is its lowest energy state, where all the electrons are in the closest possible orbitals to the nucleus. This state is significant because it is the most stable and prevalent form of the atom under normal conditions. When determining the electron configuration, it is always the ground state that is considered unless stated otherwise.

To find the ground state electron configuration, we fill the atomic orbitals with electrons following the previously mentioned principles while keeping the total number of electrons equal to the atomic number of the element. As a result, the ground state configuration provides the foundation for understanding an atom's reactivity, binding characteristics, and magnetic properties.

Atomic Orbitals

Atomic orbitals are regions in an atom where there is a high probability of finding electrons. Each orbital can hold a maximum of two electrons, which must have opposite spins according to the Pauli exclusion principle. Orbitals are organized into different shapes and energy levels, which are s, p, d, and f.

The 's' orbitals are spherical; the 'p' orbitals are dumbbell-shaped; the 'd' orbitals are more complex, and the 'f' orbitals are even more so, often not depicted due to their complexity. The arrangement of electrons in these orbitals dictates the chemical behavior and magnetism of an atom. Understanding atomic orbitals is essential in comprehending how atoms interact with magnetic fields and their tendencies to form bonds with other atoms.