The element of 4th period of the periodic table having maximum number of unpaired electrons in its ground state is

Options

A. `._(20) Ca`
B. `._(30)Zn`
C. `._(33) As`
D. `._(24)Cr`

Explanation

To determine the element of the 4th period of the periodic table that has the maximum number of unpaired electrons in its ground state, we will analyze the electronic configurations of the relevant elements in this period.

### Step-by-Step Solution:

1. **Identify the Elements in the 4th Period**:
The elements in the 4th period are:
- Potassium (K)
- Calcium (Ca)
- Scandium (Sc)
- Titanium (Ti)
- Vanadium (V)
- Chromium (Cr)
- Manganese (Mn)
- Iron (Fe)
- Cobalt (Co)
- Nickel (Ni)
- Copper (Cu)
- Zinc (Zn)

2. **Write the Electronic Configurations**:
- **Potassium (K)**: [Ar] 4s¹
- **Calcium (Ca)**: [Ar] 4s²
- **Scandium (Sc)**: [Ar] 3d¹ 4s²
- **Titanium (Ti)**: [Ar] 3d² 4s²
- **Vanadium (V)**: [Ar] 3d³ 4s²
- **Chromium (Cr)**: [Ar] 3d⁵ 4s¹
- **Manganese (Mn)**: [Ar] 3d⁵ 4s²
- **Iron (Fe)**: [Ar] 3d⁶ 4s²
- **Cobalt (Co)**: [Ar] 3d⁷ 4s²
- **Nickel (Ni)**: [Ar] 3d⁸ 4s²
- **Copper (Cu)**: [Ar] 3d¹⁰ 4s¹
- **Zinc (Zn)**: [Ar] 3d¹⁰ 4s²

3. **Count the Unpaired Electrons**:
- **Potassium (K)**: 1 unpaired electron (4s¹)
- **Calcium (Ca)**: 0 unpaired electrons (4s²)
- **Scandium (Sc)**: 3 unpaired electrons (3d¹ 4s²)
- **Titanium (Ti)**: 2 unpaired electrons (3d² 4s²)
- **Vanadium (V)**: 3 unpaired electrons (3d³ 4s²)
- **Chromium (Cr)**: 6 unpaired electrons (3d⁵ 4s¹)
- **Manganese (Mn)**: 5 unpaired electrons (3d⁵ 4s²)
- **Iron (Fe)**: 4 unpaired electrons (3d⁶ 4s²)
- **Cobalt (Co)**: 3 unpaired electrons (3d⁷ 4s²)
- **Nickel (Ni)**: 2 unpaired electrons (3d⁸ 4s²)
- **Copper (Cu)**: 1 unpaired electron (3d¹⁰ 4s¹)
- **Zinc (Zn)**: 0 unpaired electrons (3d¹⁰ 4s²)

4. **Identify the Maximum**:
From the counts above, the element with the maximum number of unpaired electrons is **Chromium (Cr)**, which has 6 unpaired electrons.

### Conclusion:
The element of the 4th period of the periodic table having the maximum number of unpaired electrons in its ground state is **Chromium (Cr)**.

---