Second electron affinity of oxygen is ............ .

Explanation

To determine the second electron affinity of oxygen, we need to follow these steps:

### Step 1: Understand the Definition of Second Electron Affinity
The second electron affinity refers to the energy change that occurs when an electron is added to a negatively charged ion (an anion) to form a more negatively charged ion. It can be represented as:
\[ \text{O}^- (g) + e^- \rightarrow \text{O}^{2-} (g) \]

### Step 2: Identify the First Electron Affinity of Oxygen
The first electron affinity of oxygen is the energy released when an electron is added to a neutral oxygen atom to form a negative ion (O⁻). This value is approximately -142 kJ/mol, indicating that energy is released during this process.
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