Which of the following electron configurations is correct for iron,(atomic number26)?

Options

A. [kr]`4s^(1)3d^(6)`
B. [kr]`4s^(1)3d^(7)`
C. [Ar]`4s^(2)3d^(6)`
D. [kr]`4s^(2)3d^(6)`

Answer

To determine the correct electron configuration for iron (Fe), which has an atomic number of 26, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number**:
- The atomic number of iron (Fe) is 26. This means that an iron atom has 26 electrons.

2. **Understand Electron Configuration**:
- Electrons are filled into atomic orbitals following the Aufbau principle, which states that electrons occupy the lowest energy orbitals first.

3. **Fill the Orbitals**:
- The order of filling the orbitals is as follows:
- 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.
- For iron, we fill the orbitals in this order until we reach 26 electrons:
- 1s² (2 electrons)
- 2s² (2 electrons)
- 2p⁶ (6 electrons)
- 3s² (2 electrons)
- 3p⁶ (6 electrons)
- 4s² (2 electrons)
- 3d⁶ (6 electrons)

4. **Count the Electrons**:
- Total electrons filled:
- 1s² + 2s² + 2p⁶ + 3s² + 3p⁶ + 4s² + 3d⁶ = 2 + 2 + 6 + 2 + 6 + 2 + 6 = 26 electrons.

5. **Express in Noble Gas Configuration**:
- The electron configuration can also be expressed using the noble gas preceding iron, which is argon (Ar), with an atomic number of 18.
- Thus, the electron configuration of iron can be written as:
- [Ar] 4s² 3d⁶

6. **Select the Correct Option**:
- From the options given, the correct electron configuration for iron is:
- **C: [Ar] 4s² 3d⁶**

### Summary:
The correct electron configuration for iron (atomic number 26) is [Ar] 4s² 3d⁶.