Question

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?

• A. The reactivity decreases in the alkali metals but increases in the halogens with increase in atomic number down the group
• B. In both the alkali metals and the halogens the chemical reactivity decreases with increase in atomic number down the group
• C. Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens
• D. In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic number down the group

Answer 1

The correct option is D In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic number down the group

In alkali, as we move down the group size increases thus an ability to lose electrons increases thus reactivity increases.

But in the case of halogens, the reactivity decreases because of the following reasons:

• Due to the decrease in electronegativity down the group.
• Decrease in oxidizing ability due to the inert pair effect.
• Increase in atomic radius down the group which lessens the attraction of valence electron of other atoms thus decreasing reactivity.