What is the most common oxidation state of first transition series?

Explanation

To determine the most common oxidation state of the first transition series (3d series), we can follow these steps:

### Step 1: Identify the Elements in the First Transition Series
The first transition series includes the following elements:
- Scandium (Sc)
- Titanium (Ti)
- Vanadium (V)
- Chromium (Cr)
- Manganese (Mn)
- Iron (Fe)
- Cobalt (Co)
- Nickel (Ni)
- Copper (Cu)
- Zinc (Zn)

### Step 2: Write the General Electronic Configuration
The general electronic configuration for the first transition series can be expressed as:
\[ \text{[Ar]} \, 3d^{1-10} \, 4s^{0-2} \]
This indicates that the d-orbitals are progressively filled from 1 to 10 electrons while the s-orbital can hold 0 to 2 electrons.

### Step 3: Determine the Electronic Configuration of Each Element
Now, we will write the specific electronic configuration for each element:
- Sc: \( [Ar] \, 3d^1 \, 4s^2 \)
- Ti: \( [Ar] \, 3d^2 \, 4s^2 \)
- V: \( [Ar] \, 3d^3 \, 4s^2 \)
- Cr: \( [Ar] \, 3d^5 \, 4s^1 \) (notable exception)
- Mn: \( [Ar] \, 3d^5 \, 4s^2 \)
- Fe: \( [Ar] \, 3d^6 \, 4s^2 \)
- Co: \( [Ar] \, 3d^7 \, 4s^2 \)
- Ni: \( [Ar] \, 3d^8 \, 4s^2 \)
- Cu: \( [Ar] \, 3d^{10} \, 4s^1 \) (notable exception)
- Zn: \( [Ar] \, 3d^{10} \, 4s^2 \)

### Step 4: Analyze the Common Oxidation States
From the electronic configurations, we can see that:
- Most elements can lose 2 electrons (the 4s electrons) easily, leading to a common oxidation state of +2.
- Chromium and Copper, despite having unique configurations, can also exhibit a +2 oxidation state.

### Step 5: Conclusion
The most common oxidation state of the first transition series is +2.