Which of these is the correct electronic configuration of Platinum (At. Number 78)

Options

A. `[Xe]4f^(14) 5d^(9) 6s^(1)`
B. `[Xe]4f^(13) 5d^(9) 6s^(1)`
C. `[Xe]4f^(14) 5d^(10) 6s^(0)`
D. `[Xe]4f^(14) 5d^(8) 6s^(2)`

Explanation

To determine the correct electronic configuration of Platinum (Pt), which has an atomic number of 78, we can follow these steps:

### Step 1: Understand the Aufbau Principle
The Aufbau principle states that electrons fill atomic orbitals in order of increasing energy levels. We will start filling from the lowest energy level to the highest.

### Step 2: Write the Expected Electronic Configuration
Following the Aufbau principle, we can write the expected electronic configuration for Platinum:
1. Fill the 1s orbital: 1s²
2. Fill the 2s orbital: 2s²
3. Fill the 2p orbitals: 2p⁶
4. Fill the 3s orbital: 3s²
5. Fill the 3p orbitals: 3p⁶
6. Fill the 4s orbital: 4s²
7. Fill the 3d orbitals: 3d¹⁰
8. Fill the 4p orbitals: 4p⁶
9. Fill the 5s orbital: 5s²
10. Fill the 4d orbitals: 4d¹⁰
11. Fill the 5p orbitals: 5p⁶
12. Fill the 6s orbital: 6s²
13. Fill the 4f orbitals: 4f¹⁴
14. Fill the 5d orbitals: 5d⁹ (expected)

So, the expected configuration would be:
\[ \text{1s}^2 \, \text{2s}^2 \, \text{2p}^6 \, \text{3s}^2 \, \text{3p}^6 \, \text{4s}^2 \, \text{3d}^{10} \, \text{4p}^6 \, \text{5s}^2 \, \text{4d}^{10} \, \text{5p}^6 \, \text{6s}^2 \, \text{4f}^{14} \, \text{5d}^9 \]

### Step 3: Identify the Actual Configuration
However, Platinum is an exception to the expected configuration due to stability reasons. The actual electronic configuration of Platinum is:
\[ \text{1s}^2 \, \text{2s}^2 \, \text{2p}^6 \, \text{3s}^2 \, \text{3p}^6 \, \text{4s}^2 \, \text{3d}^{10} \, \text{4p}^6 \, \text{5s}^2 \, \text{4d}^{10} \, \text{5p}^6 \, \text{6s}^1 \, \text{4f}^{14} \, \text{5d}^9 \]

### Step 4: Conclusion
Thus, the correct electronic configuration of Platinum (Pt) is:
\[ \text{[Xe]} \, \text{6s}^1 \, \text{4f}^{14} \, \text{5d}^9 \]