KCET 2014 Chemistry Solved Paper

Lewis acid strength decreases down the group therefore,order is BCl3>AlCl3>GaCl3 First ionization energy for Group 13 elements decreases down the group till Al then increases for Ga due to d-electron contraction, decrease for In, then again increases for Tl due to lanthanoid contraction, that is, B > Tl > Ga > Al > In.
Inert pair effect shown by heavier elements only, therefore, for Tl, +1 oxidation states in more stable and it strong oxidizing agent in +3 states.