Consider the following equation: Al3+1g2 + e-¡Al2+1g2 Which of the following statements are true? (i) The energy change for this process is the second electron affinity of Al atom since Al2+1g2 is formed. (ii) The energy change for this process is the negative of the third ionization energy of the Al atom. (iii) The energy change for this process is the electron affinity of the Al2+ ion.

Verified step by step guidance

1. Identify the process described in the equation: Al^{3+}(g) + e^- \rightarrow Al^{2+}(g).
2. Understand that this process involves the addition of an electron to the Al^{3+} ion, forming Al^{2+}.
3. Recognize that electron affinity refers to the energy change when an electron is added to a neutral atom or ion. Here, an electron is added to a positively charged ion, Al^{3+}.
4. Consider the definition of ionization energy, which is the energy required to remove an electron from an atom or ion. The reverse process (adding an electron) would involve the negative of the ionization energy.
5. Evaluate each statement: (i) is incorrect because electron affinity typically refers to neutral atoms, not ions like Al^{2+}. (ii) is correct because the process is the reverse of the third ionization (removal of the third electron), so it involves the negative of the third ionization energy. (iii) is incorrect because electron affinity is not typically used for cations like Al^{2+}.

Key Concepts

Ionization Energy

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. In the context of aluminum, the first, second, and third ionization energies refer to the energy needed to remove the first, second, and third electrons, respectively. Understanding these energies is crucial for analyzing the energy changes associated with the formation of ions, such as Al2+ and Al3+.

Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase, forming a negative ion. For aluminum, the electron affinity of Al2+ refers to the energy change when an electron is added to Al2+ to form Al+. This concept is essential for evaluating the energy changes in the given reaction and determining the validity of the statements regarding electron affinity.

Second Electron Affinity

The second electron affinity refers to the energy change associated with adding an electron to a negatively charged ion, such as Al2-. This process is typically endothermic, meaning it requires energy input. Recognizing this concept is important for understanding the implications of the statements in the question, particularly regarding the energy changes involved in the transition from Al3+ to Al2+.