Which of the following sequence is correct here?

Options

A. `Tl lt ln lt Ga lt Al` (stability of + 1 oxidation state)
B. `CO_2 lt SiO_2 lt SnO_2 lt PbO_2` (increasing oxidising power)
C. `BF_3 lt BCl_3 lt B Br_3 lt Bl_3` (the lewis acid strength)
D. Both B and C

Answer

To solve the question regarding the correct sequence of stability of oxidation states and oxidizing power, we will analyze the options provided step by step.

### Step 1: Analyze the first sequence (Tl, In, Ga, Al) regarding stability of +1 oxidation state
- **Observation**: The elements given are Thallium (Tl), Indium (In), Gallium (Ga), and Aluminum (Al).
- **Trend**: As we move down the group in the periodic table, the stability of the +1 oxidation state increases due to the inert pair effect. This means that the s-electrons (which are not involved in bonding) lead to a preference for the lower oxidation state.
- **Conclusion**: The order of stability of +1 oxidation state is:
- Al < Ga < In < Tl
- **Result**: This sequence is incorrect as stated in the question.

### Step 2: Analyze the second sequence (CO2, SiO2, SnO2, PbO2) regarding oxidizing power
- **Observation**: The compounds are Carbon Dioxide (CO2), Silicon Dioxide (SiO2), Tin Dioxide (SnO2), and Lead Dioxide (PbO2).
- **Trend**: The oxidizing power increases down the group as the stability of the +4 oxidation state decreases, and the +2 state becomes more stable. Therefore, the oxidizing power increases as we go from CO2 to PbO2.
- **Conclusion**: The order of increasing oxidizing power is:
- CO2 < SiO2 < SnO2 < PbO2
- **Result**: This sequence is correct.

### Step 3: Analyze the third sequence (BF3, BCl3, BBr3, BI3) regarding Lewis acid strength
- **Observation**: The compounds are Boron Trifluoride (BF3), Boron Trichloride (BCl3), Boron Tribromide (BBr3), and Boron Triiodide (BI3).
- **Trend**: The strength of Lewis acids decreases due to the extent of backbonding. BF3 has the most backbonding due to the small size of F and its high electronegativity, making it a weaker Lewis acid. Conversely, BI3 has the least backbonding and thus is a stronger Lewis acid.
- **Conclusion**: The order of Lewis acid strength is:
- BI3 > BBr3 > BCl3 > BF3
- **Result**: This sequence is correct.

### Final Conclusion
- The correct sequences from the analysis are:
- For stability of +1 oxidation state: Al < Ga < In < Tl (incorrect as per the question)
- For oxidizing power: CO2 < SiO2 < SnO2 < PbO2 (correct)
- For Lewis acid strength: BI3 > BBr3 > BCl3 > BF3 (correct)

Thus, the correct answer to the question is option 4, which states that both the second and third sequences are correct.

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