Arrange the halogens F2,Cl2,Br2,I2, in order of their increasing reactivity with alkanes:
1.
I2<Br2<Cl2<F2
2.
Br2<Cl2<F2<I2
3.
F2<Cl2<Br2<I2
4.
Br2<I2<Cl2<F2
HINT- High electronegativity means high reactivity with alkanes
EXPLAINATION (1)
Alkane react with F2 is vigorously and with I2 the reaction is too slow that it requires a catalyst. It is because of high electronegativity of fluorine. Reactivity decreases with decrease in electronegativity and electronegativity decreases down the group.