Which of the following has smallest radius?

Options

A. `1s^(2), 2s^(2)2p^(6), 3s^(2)`
B. `1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(1)`
C. `1s^(2), 2s^(2)2p^(6),3s^(2)3p^(5)`
D. `1s^(2),2s^(2)2p^(6),3s^(2)3p^(3)`

Answer

To determine which of the given options has the smallest atomic radius, we can follow these steps:

### Step 1: Identify the Electron Configurations
The outermost electronic configurations of the given options are:
- Option 1: 3s²
- Option 2: 3s² 3p¹
- Option 3: 3s² 3p⁵
- Option 4: 3s² 3p³

### Step 2: Determine the Period
All the given options belong to the same period, which is the third period of the periodic table.

### Step 3: Understand the Trend in Atomic Radius
As we move from left to right across a period in the periodic table:
- The number of protons (nuclear charge) increases.
- The number of electrons also increases, but they are added to the same energy level (shell).
- The increased nuclear charge pulls the electrons closer to the nucleus, resulting in a decrease in atomic radius.

### Step 4: Analyze the Options
- **Option 1 (3s²)**: This is Magnesium (Mg).
- **Option 2 (3s² 3p¹)**: This is Aluminum (Al).
- **Option 3 (3s² 3p⁵)**: This is Chlorine (Cl).
- **Option 4 (3s² 3p³)**: This is Phosphorus (P).

### Step 5: Compare the Atomic Sizes
- As we move from Mg (left) to Cl (right), the atomic radius decreases.
- Chlorine (Cl), being the furthest to the right in this list, will have the smallest radius due to the highest nuclear charge attracting the outermost electrons more strongly.

### Conclusion
The element with the smallest radius among the given options is **Option 3: 3s² 3p⁵ (Chlorine)**.

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