In valence bond theory, ligand cl- donates 1 electron in ticl3, pcl3, SF6 hybridization and cl- donates 2 electron in (ptcl4)2-, (nicl4)2- hybridization....Please give me answer that the donation of number of electron depend on which factors??????

An electron giving gathering expands steadiness of a positive charge since it gives electron thickness into the decidedly charged focus. A positive charge shows electron insufficiency, and normally recommends diminished solidness contrasted with an impartial focus. by having an electron giving gathering, the successful positive charge is decreased, therefore giving soundness. 

Negative charges are balanced out by the nearness of electron pulling back gatherings, for precisely the same that positive charges are settled by electron giving gatherings.