JEE MAIN - Chemistry (2006 - No. 48)
Following statements regarding the periodic trends of chemical reactivity of the alkali metals and the
halogens are given. Which of these statements gives the correct picture?
The reactivity decreases in the alkali metals but increases in the halogens with increase in atomic
number down the group
In both the alkali metals and the halogens the chemical reactivity decreases with increase in
atomic number down the group
Chemical reactivity increases with increase in atomic number down the group in both the alkali
metals and halogens
In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic
number down the group
Explanation
For alkali metals on going down the group, number of electron shells increase, so forces between the oppositely charged electron and nucleus is less so electron can be removed easily, therefore, reactivity increases. But for halogens they react by abstracting electron from less electronegative atoms and the attraction for additional electron is stronger when there are fewer filled electron shells between the valence electrons and atomic nucleus.
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