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?

  • Option 1)

    The reactivity decreases in the alkali metals but increases in the halogens with increase in atomic number down the group

  • Option 2)

    In both the alkali metals and the halogens the chemical reactivity decreases with increase in atomic number down the group

  • Option 3)

    Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens

  • Option 4)

    In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic number down the group

 

Answers (1)
V Vakul

As we learnt in

Electropositive or metallic character of alkaline earth metal -

On account of their relatively low ionisation energies, the alkaline earth metal has a strong tendency to lose both the valence electrons to form dispositive cations.thus these elements show strong electropositive or metallic character.

-

 

 and

Periodic trend and chemical reactivity -

The maximum chemical reactivity at extreme right (among halogens) shown by the gain of an electron forming an anion.

-

 

In Alkali metals, tendency is to lose electron, hence the reactivity increases down the group. Whereas in halogens, tendency is to gain electron which is highest at the top and falls down the group.


Option 1)

The reactivity decreases in the alkali metals but increases in the halogens with increase in atomic number down the group

This option is incorrect.

Option 2)

In both the alkali metals and the halogens the chemical reactivity decreases with increase in atomic number down the group

This option is incorrect.

Option 3)

Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens

This option is incorrect.

Option 4)

In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic number down the group

This option is correct.

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