Which of the following orders is (are) correct for size:

Options

A. `AI ~~ Ga`
B. `Te^(2-) gt I^(-) gt Cs^(+) gt Ba^(2+)`
C. `Cr^(3+) lt Cr^(6+)`
D. `Pd ~~ Pt`

Explanation

To determine the correct order of sizes for the given elements, we will analyze each pair based on their positions in the periodic table and the effects of electron removal or addition on their sizes.

### Step-by-Step Solution:

1. **Compare Aluminum (Al) and Gallium (Ga)**:
- Both Al and Ga are in Group 13, with Al in the 3rd period and Ga in the 4th period.
- Generally, size increases down a group. However, Ga has a filled 3d subshell which causes a contraction due to d-orbital shielding.
- Thus, the size order is: **Al > Ga**.

2. **Analyze the Cation and Anion Sizes**:
- When comparing anions and cations, anions are larger than their neutral atoms, while cations are smaller.
- For the elements given: Te²⁻ > I⁻ > Cs⁺ > Ba²⁺.
- This is because Te²⁻ has the most electrons (and thus the largest size), while Ba²⁺ has lost two electrons and is the smallest.

3. **Compare Chromium Ions (Cr³⁺ and Cr⁶⁺)**:
- Cr³⁺ has lost 3 electrons, while Cr⁶⁺ has lost 6 electrons.
- The more electrons removed, the smaller the ion becomes due to increased effective nuclear charge on the remaining electrons.
- Therefore, the size order is: **Cr³⁺ > Cr⁶⁺**.

4. **Compare Nickel (Ni), Palladium (Pd), and Platinum (Pt)**:
- As we move down the group, size generally increases. However, due to lanthanide contraction, the size of Pt is smaller than expected.
- The order is: **Ni < Pd ≈ Pt** (Pd and Pt are approximately equal in size).

### Final Summary of Correct Orders:
- **Order 1**: Al > Ga (Correct)
- **Order 2**: Te²⁻ > I⁻ > Cs⁺ > Ba²⁺ (Correct)
- **Order 3**: Cr³⁺ > Cr⁶⁺ (Incorrect as given in the question)
- **Order 4**: Ni < Pd ≈ Pt (Correct)

### Conclusion:
The correct orders are from options 1, 2, and 4. Option 3 is incorrect.

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