Following statements regarding the periodic trends of chemical reactivity of the alkali metals and the halogens are given. Which of the following statement is correct?
A
Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens.
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B
In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic number down the group.
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C
The reactivity decreases in the alkali metals but increases in the halogens with increase in atomic number
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D
In both the alkali metals and the halogens, the chemical reactivity decreases with increase in atomic number down the group.
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Solution
The correct option is B In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic number down the group. In alkali metals, the reactivity increases down the group due to a decrease in first ionization enthalpy.
But in the case of halogens, the reactivity decreases down the group due to a decrease in their electron gain enthalpy.