a. Write an equation for the second electron affinity of chlorine.
b. Would you predict a positive or a negative quantity for this process?

검증된 단계별 안내

Step 1: Understand the concept of electron affinity. Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase to form a negative ion. The first electron affinity is usually exothermic (releases energy) because the added electron is attracted to the positively charged nucleus.

Step 2: Define the second electron affinity. The second electron affinity refers to the energy change when an additional electron is added to a negatively charged ion. This process is generally endothermic (requires energy) because the added electron experiences repulsion from the negatively charged ion.

Step 3: Write the chemical equation for the second electron affinity of chlorine. Start with the chloride ion (Cl^-) and add an electron to form the Cl^2- ion: \[ \text{Cl}^- (g) + e^- \rightarrow \text{Cl}^{2-} (g) \]

Step 4: Predict the sign of the second electron affinity. Since the second electron is being added to an already negatively charged ion, it will experience repulsion, making the process endothermic. Therefore, the second electron affinity is expected to be a positive quantity.

Step 5: Summarize the findings. The second electron affinity of chlorine involves adding an electron to Cl^- to form Cl^2-, and this process is endothermic, resulting in a positive energy change.

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주요 개념

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Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. For most elements, this process releases energy, resulting in a negative value for electron affinity. However, the second electron affinity refers to the addition of a second electron to an already negatively charged ion, which typically requires energy input due to the repulsion between the negatively charged particles.

Chlorine's Electron Configuration

Chlorine has an atomic number of 17, with an electron configuration of [Ne]3s²3p⁵. When it gains one electron, it achieves a stable noble gas configuration, becoming Cl⁻. The addition of a second electron to Cl⁻ (to form Cl²⁻) encounters increased electron-electron repulsion, making this process less favorable and typically resulting in a positive electron affinity value.

Energy Considerations in Ion Formation

The energy associated with ion formation is crucial in determining whether a process is exothermic or endothermic. For the first electron affinity of chlorine, energy is released, making it negative. However, for the second electron affinity, energy must be supplied to overcome the repulsion between the negatively charged ion and the incoming electron, leading to a positive value for this process.

a. Write an equation for the second electron affinity of chlorine.b. Would you predict a positive or a negative quantity for this process?