Which of the following electronic configuration is not possible? 

Options

A. `1s^(2)2s^(2) 2p^(6)`
B. `1s^(2)2s^(2)2p^(7)`
C. `1s^(2)2s^(2)`
D. `1s^(2)2s^(2)2p^(5)`

Answer

To determine which electronic configuration is not possible, we need to analyze the given configurations based on the rules of electron filling in atomic orbitals. Here’s the step-by-step solution:

### Step 1: Understand the Maximum Electron Capacity of Orbitals
- **s orbital**: Can hold a maximum of 2 electrons.
- **p orbital**: Can hold a maximum of 6 electrons (3 sub-levels, each can hold 2 electrons).
- **d orbital**: Can hold a maximum of 10 electrons (5 sub-levels, each can hold 2 electrons).
- **f orbital**: Can hold a maximum of 14 electrons (7 sub-levels, each can hold 2 electrons).

### Step 2: Analyze the Given Configurations
Let's assume the options provided are:
1. 1s² 2s² 2p⁶
2. 1s² 2s² 2p⁷
3. 1s² 2s² 2p⁶ 3s²
4. 1s² 2s² 2p⁵

### Step 3: Identify the Invalid Configuration
- **Option 1**: 1s² 2s² 2p⁶ is valid (2 + 2 + 6 = 10 electrons).
- **Option 2**: 1s² 2s² 2p⁷ is **not valid** because the p orbital can only hold a maximum of 6 electrons.
- **Option 3**: 1s² 2s² 2p⁶ 3s² is valid (2 + 2 + 6 + 2 = 12 electrons).
- **Option 4**: 1s² 2s² 2p⁵ is valid (2 + 2 + 5 = 9 electrons).

### Conclusion
The electronic configuration that is not possible is **Option 2: 1s² 2s² 2p⁷**.