JEE MAIN - Chemistry (2007 - No. 11)
The stability of dihalides of $$Si,Ge,Sn$$ and $$Pb$$ increases steadily in the sequence :
$$Pb{X_2} < < Sn{X_2} < < Ge{X_2} < < Si{X_2}$$
$$Ge{X_2} < < Si{X_2} < < Sn{X_2} < < Pb{X_2}$$
$$Si{X_2} < < Ge{X_2} < < Pb{X_2} < < Sn{X_2}$$
$$Si{X_2} < < Ge{X_2} < < Sn{X_2} < < Pb{X_2}$$
Explication
Reductance of valence shell electrons to participate in bonding is called inert pair effect. The stability of lower oxidation state ($${ + 2\,\,}$$ for group $$14$$ element) increases on going down the group. So the correct order is
$$Si{X_2} < Ge{X_2} < Sn{X_2} < Pb{X_2}$$
$$Si{X_2} < Ge{X_2} < Sn{X_2} < Pb{X_2}$$