Question

Choose the best response for the following. The ionization energy for the chlorine atom is equal in magnitude to the electron affinity for a. the \(\mathrm{Cl}\) atom. b. the \(\mathrm{Cl}^{-}\) ion. c. the \(\mathrm{Cl}^{+}\) ion. d. the \(\mathrm{F}\) atom. e. none of these. Explain each choice. Justify your choice, and for the choices you did not select, explain what is incorrect about them.

Short answer

The correct answer is option b: the electron affinity of the Cl^- ion. The ionization energy of the Cl atom is equal in magnitude to the electron affinity of the Cl^- ion, as both processes involve a single electron interacting with chlorine.

Step-by-step solution

Option a: The Cl atom

We know that the ionization energy for the Cl atom is the energy required to remove an electron from the Cl atom. The electron affinity for the Cl atom is the energy released when an electron is added to the Cl atom. Since ionization energy and electron affinity have opposite effects (removal vs addition of an electron), they are not equal in magnitude for the Cl atom.

Option b: The Cl- ion

The electron affinity of the Cl^- ion is the energy change when an electron is added to Cl^- to form Cl^2-. However, when comparing this to the ionization energy of the Cl atom (which involves the removal of an electron), it is important to note that both processes involve the energy change of a single electron interacting with chlorine. Therefore, the ionization energy of the Cl atom is equal in magnitude to the electron affinity of the Cl^- ion.

Option c: The Cl+ ion

The electron affinity of the Cl^+ ion is the energy change when an electron is added to Cl^+ to form Cl. However, the energy is different when adding an electron to Cl^+ than when removing an electron from neutral Cl. Thus, the ionization energy of Cl atom is not equal in magnitude to the electron affinity of the Cl^+ ion.

Option d: The F atom

The ionization energy of the chlorine atom is the energy required to remove an electron from the Cl atom, while the electron affinity of the F atom is the energy released when an electron is added to the F atom. These two atoms have different energy levels and cannot be directly compared.

Option e: None of these

Since we've found that the ionization energy of the Cl atom is equal to the electron affinity of the Cl^- ion in Option b, we can discard this option as a possibility.

Conclusion

The correct answer is option b: the electron affinity of the Cl^- ion. The ionization energy of the Cl atom is equal in magnitude to the electron affinity of the Cl^- ion, as both processes involve a single electron interacting with chlorine.

Key concepts

Electron Affinity

Electron affinity is a measure of how much energy is released when an electron is added to a neutral atom in the gaseous state. In simpler terms, it's how much an atom "wants" an extra electron. Different atoms will attract electrons with varying strengths based on their electronic configuration.

Some important points about electron affinity include:

• Atoms with nearly full outer shells typically have higher electron affinity values.
• Electron affinity can be negative or positive, depending on whether the process releases or absorbs energy.
• In many cases, a higher electron affinity indicates stronger attraction between the added electron and the nucleus.

Understanding electron affinity helps us predict how atoms interact with each other, particularly in forming ions.

Chlorine Atom

A chlorine atom is found in group 17 of the periodic table, also known as the halogens. It has an atomic number of 17, meaning it has 17 protons and, when neutral, 17 electrons. Chlorine is highly reactive, as it seeks to gain one more electron to achieve a full outer electron shell like that of a noble gas.

Key characteristics of chlorine include:

• Appearance: Greenish-yellow gas at room temperature.
• Reactivity: Very high, especially with metals and other nonmetals to form salts.
• Electron configuration: [Ne] 3s² 3p⁵, lacking one electron to fill the 3p orbital.

The reactivity of chlorine, related to its need for electrons, makes it an excellent example for studying concepts like electron affinity and ionization.

Chloride Ion

The chloride ion, \( ext{Cl}^-\), is formed when a chlorine atom gains an extra electron. This process speaks directly to the concept of electron affinity, where the chlorine atom releases energy upon gaining this electron to become more stable.

Here are some essential facts about the chloride ion:

• Charge: Negative one, since it has gained one addition electron.
• Stability: More stable than a neutral chlorine atom due to the completion of its outer electron shell.
• Role in nature: Common in salts, such as sodium chloride (table salt), and important in biological systems for maintaining fluid balance.

The formation of the chloride ion is a prime example of how atoms achieve stability through electron transfer.

Energy Change in Atoms

Energy changes occur in atoms primarily through processes such as ionization and electron affinity. These changes are central to understanding chemical reactions and bonding.

Some important points about energy changes in atoms include:

• Ionization Energy: The energy required to remove an electron from an atom, usually making the atom a positive ion.
• Relationship: The ionization energy and electron affinity can be thought of as opposite processes - removal vs. addition of an electron.
• Energy magnitude: A higher ionization energy means it requires more energy to remove an electron; a high electron affinity means energy is released efficiently when an electron is added.

Understanding these energy changes helps in predicting the behavior of atoms during chemical interactions and reactions.