How can you explain higher stability of BCl_3 as compared to TlCl_3 ?

1.	How can you explain higher stability of BCl_3 as compared to TlCl_3 ?
Answer» Solution :Boron and thallium belong to group 13 of the PERIODIC table. In this group, the +1 oxidation state becomes more STABLE on moving down the group. `BCl_3` is more stable than `TlCl_3`, because the +3 oxidation state more stable than the +3 oxidation state of Tl. In Tl, the +3 state is highly OXIDISING and it reverts BACK to the more stable +1 state.

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