To determine the correct order of atomic or ionic radii among the given elements, we need to analyze the trends in atomic radii across the periodic table, particularly focusing on the transition metals and their ionic forms.
### Step-by-Step Solution:
1. **Identify the Elements**: The elements mentioned are Scandium (Sc), Titanium (Ti), Vanadium (V), and Chromium (Cr). These are all transition metals.
2. **Understand the Trend in Atomic Radii**:
- Atomic radii generally decrease across a period from left to right due to the increase in nuclear charge (more protons in the nucleus) which pulls the electrons closer to the nucleus.
- In the case of transition metals, as we move from Sc to Ti to V to Cr, the electrons are added to the d-orbitals. The effective nuclear charge increases, leading to a decrease in atomic radii.
3. **Electronic Configurations**:
- Scandium (Sc): [Ar] 3d¹ 4s²
- Titanium (Ti): [Ar] 3d² 4s²
- Vanadium (V): [Ar] 3d³ 4s²
- Chromium (Cr): [Ar] 3d⁵ 4s¹
As we can see, the d-electrons increase while the 4s electrons remain the same until we reach chromium, where the configuration changes slightly.
4. **Analyze the Atomic Radii**:
- From Sc to Ti, the atomic radius decreases.
- From Ti to V, the atomic radius continues to decrease.
- From V to Cr, the atomic radius also decreases, but the rate of decrease can vary due to electron-electron repulsions in the d-orbitals.
5. **Comparing Ionic Radii**:
- When considering anions, the size of the ion increases with the addition of negative charges. For example, among anions like S²⁻, O²⁻, and Cl⁻, the size increases with the charge.
- The order of ionic radii for anions is typically: N³⁻ > O²⁻ > F⁻ > Ne (increasing negative charge leads to larger radii).
6. **Conclusion**: Based on the analysis, the correct order of atomic/ionic radii from Sc to Cr is decreasing. Therefore, the correct order of atomic/ionic radii is:
- Sc > Ti > V > Cr
### Final Answer:
The correct order of atomic/ionic radii is: **Sc > Ti > V > Cr**.
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