To solve the question regarding the correct sequence of stability of oxidation states, oxidizing power, and Lewis acid strength, we will analyze each part step by step.
### Step 1: Stability of +1 Oxidation State in Group 13 Elements
1. **Identify the elements**: The group 13 elements mentioned are Aluminium (Al), Gallium (Ga), Indium (In), and Thallium (Tl).
2. **Understand oxidation states**: These elements can exhibit +1 and +3 oxidation states. The stability of the +1 oxidation state increases down the group due to the inner pair effect.
3. **Order the stability**:
- Aluminium (Al) has the least stability for +1 due to its tendency to form +3.
- Thallium (Tl) has the highest stability for +1 due to the inert pair effect.
4. **Conclusion**: The correct order of stability is: Tl > In > Ga > Al. Thus, the statement "thallium < indium < gallium < aluminium" is incorrect.
### Step 2: Oxidizing Power of Oxides
1. **Identify the oxides**: The oxides in question are CO2, SiO2, SnO2, and PbO2.
2. **Understand oxidizing power**: Oxidizing power refers to the ability of a substance to gain electrons (be reduced). As we move down the group, the stability of the higher oxidation state decreases, leading to increased oxidizing power.
3. **Order the oxidizing power**:
- CO2 has the least oxidizing power.
- PbO2 has the highest oxidizing power because lead can readily be reduced from +4 to +2.
4. **Conclusion**: The correct order is: CO2 < SiO2 < SnO2 < PbO2. Thus, this statement is correct.
### Step 3: Lewis Acid Strength of Boron Compounds
1. **Identify the compounds**: The compounds are BF3, BCl3, BBr3, and BI3.
2. **Understand Lewis acid strength**: Lewis acids accept electron pairs. The strength of Lewis acids can be influenced by back bonding.
3. **Analyze back bonding**:
- BF3 has strong back bonding due to effective overlap between the 2p orbitals of F and the empty p orbital of B, making it a weak Lewis acid.
- As we move to BCl3, BBr3, and BI3, the back bonding decreases due to poorer overlap (2p with 3p, 4p, and 5p respectively), increasing the Lewis acid strength.
4. **Conclusion**: The correct order of Lewis acid strength is: BF3 < BCl3 < BBr3 < BI3. Thus, this statement is also correct.
### Final Conclusion
From the analysis:
- The first sequence regarding the stability of +1 oxidation state is incorrect.
- The second sequence regarding oxidizing power is correct.
- The third sequence regarding Lewis acid strength is also correct.
Thus, the correct answer to the question is that both B and C are correct.
