How can you explainhigher stability of BCl_(3) as compared to TlCl_(3)

1.	How can you explainhigher stability of BCl_(3) as compared to TlCl_(3) ?
Answer» SOLUTION :DUE to the poor shielding of the s-electrons of the valenceshell (6s) by the 3d-,4d-,5d and 4f-electronsinertpair effect is maximumin Tl. As a resultonly `6 p^(1)`electronsparticipates in BOND formation and contrast,due to theabsenceof d-andf-electrons , B does not SHOW inertpair effect. In other words, allthe three valenceelectrons(i.e, two 2s - and one 2p-) take part in bond formationand hence Bshowsanoxidationstate of +3 and thusforms`BCl_(3)`. thus,`BCl_(3)` is more stablethan `TlCl_(3)`.

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