Which is/are the correct order/s of atomic radius?

Options

A. `Mn gt Fe gt CO`
B. `Mn ~~ Fe ~~ Co`
C. `Sc gt Ti gt V`
D. `Zn lt Cu lt Ni`

Answer

To determine the correct order of atomic radius among the D block elements, we need to analyze the trends in atomic size across the first series of D block elements (3D series) which includes the elements from scandium (Sc) to zinc (Zn).

### Step-by-Step Solution:

1. **Identify the Elements**:
The first series of D block elements includes:
- Scandium (Sc, Z=21)
- Titanium (Ti, Z=22)
- Vanadium (V, Z=23)
- Chromium (Cr, Z=24)
- Manganese (Mn, Z=25)
- Iron (Fe, Z=26)
- Cobalt (Co, Z=27)
- Nickel (Ni, Z=28)
- Copper (Cu, Z=29)
- Zinc (Zn, Z=30)

2. **Understand the Trend**:
- From Scandium to Chromium, the atomic radius decreases. This is due to the increase in effective nuclear charge (Z_eff) as we move across the period, which pulls the electrons closer to the nucleus, resulting in a smaller atomic radius.
- From Manganese to Cobalt, the atomic radius remains relatively constant. This is because the d-orbitals start to fill, and the repulsion between the electrons in the d-orbitals counteracts the increase in nuclear charge, leading to a nullification effect on atomic size.
- From Nickel to Zinc, the atomic radius increases slightly due to increased electron-electron repulsion as the d-orbitals become fully filled.

3. **Establish the Orders**:
- The expected order of atomic radius from Sc to Zn can be summarized as follows:
- Sc > Ti > V > Cr > Mn ≈ Fe ≈ Co > Ni < Cu < Zn
- Here, Mn, Fe, and Co have similar atomic radii, while Ni, Cu, and Zn show an increase in size due to electronic repulsion.

4. **Evaluate the Options**:
- Based on the trends observed:
- The order of atomic radius from Sc to Cr is correct (decreasing).
- The atomic radius of Mn, Fe, and Co is approximately equal.
- The atomic radius from Ni to Zn shows an increase.

5. **Conclusion**:
- The correct orders of atomic radius are:
- Sc > Ti > V > Cr (decreasing)
- Mn ≈ Fe ≈ Co (approximately equal)
- Ni < Cu < Zn (increasing)

### Final Answer:
The correct orders of atomic radius are only option B and option C based on the analysis above.