In first transition series elements the highest oxidation number shown is +x. What is the value of x.

Answer

To determine the highest oxidation number shown by the elements in the first transition series, we can follow these steps:

### Step 1: Identify the First Transition Series
The first transition series includes the elements from Scandium (Sc) to Zinc (Zn), which are Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

**Hint:** Remember that the first transition series consists of elements with atomic numbers 21 to 30.

### Step 2: Determine the Electronic Configuration
The electronic configuration of these elements is important for understanding their oxidation states. The general electronic configuration for the first transition series is:
- Sc: [Ar] 3d¹ 4s²
- Ti: [Ar] 3d² 4s²
- V: [Ar] 3d³ 4s²
- Cr: [Ar] 3d⁵ 4s¹ (due to stability of half-filled d subshell)
- Mn: [Ar] 3d⁵ 4s²
- Fe: [Ar] 3d⁶ 4s²
- Co: [Ar] 3d⁷ 4s²
- Ni: [Ar] 3d⁸ 4s²
- Cu: [Ar] 3d¹⁰ 4s¹ (due to stability of filled d subshell)
- Zn: [Ar] 3d¹⁰ 4s²

**Hint:** Pay attention to the exceptions in electronic configurations, especially for Cr and Cu.

### Step 3: Identify the Element with the Highest Oxidation State
Among these elements, Manganese (Mn) is known to exhibit the highest oxidation state.

**Hint:** Look for the element that can lose the maximum number of electrons.

### Step 4: Calculate the Highest Oxidation State
Manganese has the electronic configuration of [Ar] 3d⁵ 4s². In its highest oxidation state, Mn can lose all 7 of its valence electrons (5 from 3d and 2 from 4s), leading to an oxidation state of +7.

**Hint:** The highest oxidation state is typically equal to the total number of valence electrons that can be lost.

### Conclusion
Thus, the highest oxidation number shown by the elements in the first transition series is +7.

**Final Answer:** The value of x is 7.