State how SF₄ is prepared????

actiniod contarction is graeter fron element to element than lanthanoid contarction.why????

SF₆ can be prepared as under:-

 S₆ + 24 F₂ →  8 SF₆

Actinide contraction is large as compared to the lanthanide contraction . This is becuse of the 5f orbital in the actinides. 5 f  orbital has poor shielding effect as compared to the 4f orbital . Therefore the effective nuclear charge is more in case of actinides .Thus nucleus will pull the outer electrons more strongly towards itself resulting in the contraction of the size .Hence in actinides size of the element is small .