Which of the following atoms have same number of unpaired electrons ?

Options

A. Copper (Z = 29)
B. Scandium (Z = 21)
C. Manganese (Z = 25)
D. Chromium (Z = 24)

Explanation

To determine which of the following atoms have the same number of unpaired electrons, we will analyze the electronic configurations of each atom and count the unpaired electrons.

### Step-by-Step Solution:

1. **Identify the Atoms and Their Atomic Numbers**:
- Copper (Cu): Atomic number 29
- Scandium (Sc): Atomic number 21
- Manganese (Mn): Atomic number 25
- Chromium (Cr): Atomic number 24

2. **Write the Electronic Configurations**:
- **Copper (Cu)**:
- Expected: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹
- Actual: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰
- **Scandium (Sc)**:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹
- **Manganese (Mn)**:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵
- **Chromium (Cr)**:
- Expected: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴
- Actual: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵

3. **Count the Unpaired Electrons**:
- **Copper (Cu)**:
- 4s¹ has 1 unpaired electron.
- 3d¹⁰ has 0 unpaired electrons.
- Total unpaired electrons = 1.
- **Scandium (Sc)**:
- 4s² has 0 unpaired electrons.
- 3d¹ has 1 unpaired electron.
- Total unpaired electrons = 1.
- **Manganese (Mn)**:
- 4s² has 0 unpaired electrons.
- 3d⁵ has 5 unpaired electrons (one for each electron in the half-filled subshell).
- Total unpaired electrons = 5.
- **Chromium (Cr)**:
- 4s¹ has 1 unpaired electron.
- 3d⁵ has 5 unpaired electrons.
- Total unpaired electrons = 1 + 5 = 6.

4. **Compare the Number of Unpaired Electrons**:
- Copper (Cu): 1 unpaired electron
- Scandium (Sc): 1 unpaired electron
- Manganese (Mn): 5 unpaired electrons
- Chromium (Cr): 6 unpaired electrons

5. **Conclusion**:
- Copper and Scandium both have the same number of unpaired electrons (1 each).

### Final Answer:
Copper (Cu) and Scandium (Sc) have the same number of unpaired electrons.