Question

How would we describe a substance that contains only paired electrons and is weakly repelled by a magnetic field? Which of the following ions would you expect to possess similar characteristics: \(\mathrm{H}_{2}^{-}, \mathrm{Ne}_{2}^{+}, \mathrm{F}_{2}, \mathrm{O}_{2}^{2+} ?\)

Short answer

A substance with only paired electrons and weakly repelled by a magnetic field is called a diamagnetic substance. Out of the given ions \(\mathrm{H}_{2}^{-}, \mathrm{Ne}_{2}^{+}, \mathrm{F}_{2}, \mathrm{O}_{2}^{2+}\), the ions with similar characteristics to a diamagnetic substance are \(\mathrm{H}_{2}^{-}\) and \(\mathrm{F}_{2}\).

Step-by-step solution

Identify the substance with only paired electrons and weak magnetic repulsion

The substance with only paired electrons and weakly repelled by a magnetic field is called a diamagnetic substance. Diamagnetism arises from the presence of all paired electrons in the substance, causing it to be weakly repelled by an external magnetic field.

Check the electronic configuration of \(\mathrm{H}_{2}^{-}\) ion

The hydrogen atom has an atomic number of 1, so its electronic configuration is 1s^1. In a covalent bond, H atoms share electrons. In the \(\mathrm{H}_{2}^{-}\) ion, each hydrogen has one electron and gains one more from the extra negative charge, making a total of 2 electrons in bonding. Thus, the electronic configuration of the \(\mathrm{H}_{2}^{-}\) ion is 1s^2, indicating both electrons are paired. This ion has similar characteristics to a diamagnetic substance.

Check the electronic configuration of \(\mathrm{Ne}_{2}^{+}\) ion

The neon atom has an atomic number of 10, so its electronic configuration is 1s^2 2s^2 2p^6. In the \(\mathrm{Ne}_{2}^{+}\) ion, one electron is removed from the atom. The new configuration becomes 1s^2 2s^2 2p^5. All electrons are not paired, indicating this ion does not have similar characteristics to a diamagnetic substance.

Check the electronic configuration of \(\mathrm{F}_{2}\) ion

The fluorine atom has an atomic number of 9, so its electronic configuration is 1s^2 2s^2 2p^5. In \(\mathrm{F}_{2}\), each fluorine atom shares one electron with the other. Thus, the resulting electron configuration remains the same, with all fluorine electrons being paired: 1s^2 2s^2 2p^6 for each fluorine atom. So, the \(\mathrm{F}_{2}\) molecule has similar characteristics to a diamagnetic substance.

Check the electronic configuration of \(\mathrm{O}_{2}^{2+}\) ion

The oxygen atom has an atomic number of 8, so its electronic configuration is 1s^2 2s^2 2p^4. In the \(\mathrm{O}_{2}^{2+}\) ion, two electrons are removed, and the configuration becomes 1s^2 2s^2 2p^3. All electrons are not paired, indicating this ion does not have similar characteristics to a diamagnetic substance.

Conclusion

Out of the given ions \(\mathrm{H}_{2}^{-}, \mathrm{Ne}_{2}^{+}, \mathrm{F}_{2}, \mathrm{O}_{2}^{2+}\), the ions with similar characteristics to a substance with only paired electrons and weakly repelled by a magnetic field (diamagnetic) are \(\mathrm{H}_{2}^{-}\) and \(\mathrm{F}_{2}\).

Key concepts

Paired Electrons

When we talk about paired electrons, we are referring to electrons that exist in pairs within an atom or molecule. Typically, these paired electrons occupy the same orbital and have opposite spins. This means they balance each other out in terms of magnetic effects. As a result, atoms, ions, or molecules with all paired electrons are often less reactive and more stable.

• Electrons in the same orbital must have opposite spins due to the Pauli Exclusion Principle.
• The term 'paired electrons' implies that there are no unpaired electrons, which directly affects the magnetic properties of the substance.

Understanding the idea of paired electrons is crucial when studying diamagnetism because it is the presence of these pairs that causes the weak magnetic effects observed in diamagnetic substances.

Magnetic Field

A magnetic field is an invisible area around a magnetic object where magnetic forces can be detected. It is a fundamental concept in physics, representing space in which magnetic forces can act on moving charges or other magnetic objects. Within chemistry, especially when studying magnetism, the response of electrons to a magnetic field becomes pivotal.

• Magnetic fields are typically represented by field lines that show the direction of magnetic forces.
• In the context of substances, those influenced by magnetic fields can be classified based on whether they are attracted, repelled, or unaffected by the magnetic force.

The unique aspect of a magnetic field is that it can interact with the electronic configurations of atoms or ions, causing different responses depending on the presence of unpaired or paired electrons.

Electronic Configuration

The electronic configuration of an atom or ion describes how its electrons are distributed across various atomic orbitals. This configuration is crucial in determining the chemical properties and reactivity of a substance. To find the electronic configuration, we follow the order of filling the orbitals, which is governed by principles such as the Aufbau principle, Hund's Rule, and the Pauli Exclusion Principle.

• Electrons fill lower energy orbitals first.
• Different elements have unique configurations that influence their magnetic properties.

In the study of diamagnetism, electronic configuration helps us identify paired or unpaired electrons. For example, ions with all paired electrons exhibit diamagnetic behavior, as seen in the step-by-step solution analysis.

Diamagnetic Substances

Diamagnetic substances contain only paired electrons. These substances are characterized by being weakly repelled by a magnetic field. Because all electrons are paired, there is a zero net magnetic moment. This lack of a magnetic moment is why they are not attracted to magnetic fields.

• Examples include ions like \(\mathrm{H}_{2}^{-}\) and \(\mathrm{F}_{2}\).
• Diamagnetism is considered a weak form of magnetism.

Understanding diamagnetism is important in various applications, including MRI technology, which exploits the magnetic properties of atoms to create detailed images. Recognizing diamagnetic substances helps us predict how materials will behave in magnetic fields, essential for both practical applications and fundamental science.