An element in period 3 whose electron affinity is zero.

Options

A. Neon
B. Sulphur
C. Sodium
D. Argon

Explanation

To determine an element in period 3 whose electron affinity is zero, we can follow these steps:

### Step 1: Identify the elements in Period 3
The elements in Period 3 of the periodic table are:
- Sodium (Na)
- Magnesium (Mg)
- Aluminum (Al)
- Silicon (Si)
- Phosphorus (P)
- Sulfur (S)
- Chlorine (Cl)
- Argon (Ar)

### Step 2: Understand Electron Affinity
Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gaseous phase. A positive value indicates that energy is released when the electron is added, while a value of zero means that the atom does not have a tendency to gain an electron.

### Step 3: Analyze the Electron Configurations
- Sodium (Na): 1s² 2s² 2p⁶ 3s¹
- Magnesium (Mg): 1s² 2s² 2p⁶ 3s²
- Aluminum (Al): 1s² 2s² 2p⁶ 3s² 3p¹
- Silicon (Si): 1s² 2s² 2p⁶ 3s² 3p²
- Phosphorus (P): 1s² 2s² 2p⁶ 3s² 3p³
- Sulfur (S): 1s² 2s² 2p⁶ 3s² 3p⁴
- Chlorine (Cl): 1s² 2s² 2p⁶ 3s² 3p⁵
- Argon (Ar): 1s² 2s² 2p⁶ 3s² 3p⁶

### Step 4: Identify the Element with Zero Electron Affinity
From the analysis, we can see that Argon (Ar) has a complete octet (2, 8, 8). Noble gases like Argon have a stable electron configuration and do not tend to gain electrons. Therefore, Argon has an electron affinity of zero.

### Conclusion
The element in Period 3 whose electron affinity is zero is **Argon (Ar)**.

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