Problem 32 - General Chemistry: Principles and Modern Applications

Question

Is it correct to say that when a diatomic molecule loses an electron, the bond energy always decreases (that is, that the bond is always weakened)? Explain.

Step-by-Step Solution

Answer

No, it's not always correct to say that when a diatomic molecule loses an electron, the bond energy always decreases. The effect on bond energy depends on the significance of the removed electron in bonding. In some cases, the removal could lead to a more stable bonding situation.

Step 1: Understand Bond Energy

Bond energy is the amount of energy required to break one mole of a bond in a diatomic molecule. It measures the strength of a bond; the greater the bond energy, the stronger the bond.

Step 2: Consider Electron Loss from Diatomic Molecule

Removal of an electron from a diatomic molecule, also known as ionization, changes the electron configuration of the molecule, and hence its bonding situation. This change can affect bond energy.

Step 3: Assess Bond Energy After Electron Loss

Loss of an electron might result in a weakened bond, thereby reducing the bond energy, particularly if the removed electron participated significantly in the bonding. However, there can also be cases when the removal of an electron results in a rearranged electron configuration that also leads to a more stable bonding situation. Therefore, it can't be stated categorically that bond energy always decreases when a diatomic molecule loses an electron.

Key Concepts

Diatomic Molecules

Diatomic molecules are composed of two atoms that are chemically bonded together. They can be made up of the same element, such as \( ext{O}_2 \) for an oxygen molecule, or different elements like \( ext{CO} \) for carbon monoxide. These molecules are common in nature. Their formation relies on the atoms sharing electrons to achieve stability.

• Diatomic molecules can be homo-nuclear, containing two atoms of the same element.
• The hetero-nuclear diatomic molecules consist of two different elements.

Due to this bond, diatomic molecules tend to be fairly stable under normal conditions because the atoms within the molecule share electrons effectively to complete their outer electron shells. This completed shell means that diatomic molecules are often less reactive than their atomic counterparts. The chemical bond holding the atoms together is crucial and directly affects the molecule’s properties, such as its bond energy.

Electron Loss

The loss of an electron from a molecule, also known as ionization, can have various effects on a diatomic molecule. When an electron is removed, it impacts the electric balance of the molecule, potentially altering its bonding characteristics.

• This electron removal is often associated with the formation of a positively charged ion.
• The electrons in a diatomic molecule help retain its structure by overcoming repulsive forces between the positively charged nuclei.

Depending on which electron is lost, the nature of the bond can dramatically change. If a bonding electron is lost, it can weaken the bond, potentially making the bond energy decrease. In some circumstances, though, losing a certain electron can result in a new, more stable electron configuration. Therefore, predicting the exact result of electron loss on bond energy requires examining the specific role of the electron in the molecular configuration.

Ionization

Ionization is the process where an atom or molecule loses an electron, becoming charged. This event is crucial to understand in the context of diatomic molecules and bonds. Ionization affects the molecule's electronic structure by altering the electron density. The potential realignment of electrons might lead to distinct bonding situations:

• One possibility is a reduced bond strength with lower bond energy if the ionized electron was essential for holding the molecule together.
• Alternatively, a removal of an electron might lead to redistribution and stabilization of remaining electrons, potentially keeping the bond intact or even stronger.

Ionization isn't always straightforward. This reaction can vary wildly based on several factors such as the initial electron configuration, the type of atoms involved in bonding, and the external conditions like temperature and pressure.

Bond Strength

Bond strength in diatomic molecules is determined by the attractiveness of the electrons that are shared between atoms. A strong bond denotes a higher bond energy, indicating that more energy is required to break the bond. Conversely, a weaker bond has a lower bond energy. Various factors impact bond strength, which can sometimes depend on the electron configuration:

• The more shared electrons conclude a higher bond strength as they're contributing to pulling the atoms together.
• The bond length also affects the strength; shorter bonds tend to be stronger.

When an electron is removed from the molecule, it doesn’t automatically mean the bond will weaken. It can lead to both strengthening and weakening, contingent on how the electrons are reorganized after the ionization process. Thus, bond strength and its response to electron loss are intricately linked to the molecular and electronic environment.