Electronic confriguration of a transition element X in +3 oxidation states is `[Ar]3d^(5)`.
What is its atomic number?

Options

A. 25
B. 26
C. 27
D. 24

Explanation

To find the atomic number of the transition element X with an electronic configuration of `[Ar] 3d^5` in the +3 oxidation state, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given electronic configuration**: The electronic configuration provided is `[Ar] 3d^5`. This indicates that in the +3 oxidation state, the element has 5 electrons in the 3d subshell.

2. **Determine the number of electrons in the neutral atom**: In the +3 oxidation state, the element has lost 3 electrons. Therefore, to find the total number of electrons in the neutral atom, we need to add back the 3 electrons that were lost to the 5 electrons in the 3d subshell.
\[ \text{Total electrons in neutral atom} = 5 \text{ (from } 3d\text{)} + 3 \text{ (lost electrons)} = 8 \text{ electrons in the d subshell} \]

3. **Identify the noble gas core**: The configuration starts with `[Ar]`, which corresponds to the noble gas Argon. Argon has an atomic number of 18, meaning it has 18 electrons.

4. **Calculate the atomic number**: The total number of electrons in the neutral atom can be calculated as follows:
\[ \text{Atomic number} = \text{Atomic number of Argon} + \text{Electrons in d subshell} \]
\[ \text{Atomic number} = 18 + 8 = 26 \]

5. **Conclusion**: The atomic number of the transition element X is 26.

### Final Answer:
The atomic number of the transition element X is **26**.

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