Question

Which of the following species would you expect to be diamagnetic and which paramagnetic: (a) \(\mathrm{OH}^{-} ;\) (b) \(\mathrm{OH} ;(\mathrm{c}) \mathrm{NO}_{3} ;(\mathrm{d}) \mathrm{SO}_{3} ;(\mathrm{e}) \mathrm{SO}_{3}^{2-} ;(\mathrm{f}) \mathrm{HO}_{2} ?\)

Short answer

(a) \(\mathrm{OH}^{-}\) is paramagnetic, (b) \(\mathrm{OH}\) is diamagnetic, (c) \(\mathrm{NO}_{3}\) is diamagnetic, (d) \(\mathrm{SO}_{3}\) is diamagnetic, (e) \(\mathrm{SO}_{3}^{2-}\) is paramagnetic, (f) \(\mathrm{HO}_{2}\) is paramagnetic.

Step-by-step solution

Determine the electron configuration of each species

Use the periodic table to determine the electron configuration of each atom in the given species. Then combine these configurations to find the overall electron configuration of the entire species. Remember to add or subtract an electron if the species is an anion (negative charge) or a cation (positive charge).

Check if there are any unpaired electrons

Examine the electron configuration of each species. If all the electrons are paired, then the species is diamagnetic. If there is at least one unpaired electron, then the species is paramagnetic.

Assign each species as diamagnetic or paramagnetic

Based on step 2, assign each species as diamagnetic or paramagnetic.

Key concepts

Electron Configuration

Electron configuration is like a map that shows how electrons are arranged in an atom or molecule. Think of electrons as tiny particles orbiting the nucleus of an atom in specific regions called orbitals.
Each orbital can hold a certain number of electrons, and the configuration tells us how these electrons are distributed. To determine the electron configuration of a species, you need to know the number of electrons it has. This involves understanding the atomic number of each element and the charge of the molecule (if any, like in ions).
For molecules, we add up the electrons from all the constituent atoms and adjust for any overall charge. For example, a species with a negative charge means it has gained extra electrons, while a positive charge indicates a loss of electrons. By following the periodic table and filling the orbitals according to established rules, you can derive the electron configuration.
It forms the foundation for predicting other properties like reactivity and magnetism.

Unpaired Electrons

Unpaired electrons are the key to understanding whether a species is paramagnetic or diamagnetic. As you fill the orbitals with electrons, it's essential to check if they all pair up. Electrons like to pair within the same orbital, as they occupy the lowest energy state in this configuration.
Whenever you have an odd number of electrons, at least one will be unpaired. Even for an even number, they should ideally fill all orbitals symmetrically. This subtle detail hints at whether a species exhibits magnetic properties.
If there are one or more unpaired electrons, that species becomes paramagnetic. It will be attracted to a magnetic field. However, if every electron is paired, the species is diamagnetic and will actually be repelled by a magnetic field.
Hence, identifying unpaired electrons from the electron configuration is crucial in predicting magnetic behavior.

Magnetic Properties

Diamagnetism and paramagnetism are two important concepts related to the magnetic properties of substances. They arise due to the arrangement and behavior of electrons. **Diamagnetism**
Diamagnetic substances have all their electrons paired. This results in no net magnetic moment because the magnetic fields from paired electrons cancel each other out.
This makes diamagnetic substances weakly repelled by external magnetic fields. **Paramagnetism**
Paramagnetic substances have one or more unpaired electrons. Unlike diamagnetic substances, the unpaired electrons contribute to a net magnetic moment. Therefore, these substances are attracted to magnetic fields.
The strength of paramagnetism depends on the number of unpaired electrons: more unpaired electrons lead to stronger attraction. Understanding these properties allows scientists to predict the response of materials in magnetic environments, which is useful in numerous technological and industrial applications.