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The S-Block Elements

Question
CBSEENCH11007076
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How will you explain that alkali metals are chemically highly receive?

Solution

Due to low values of first ionisation enthalpies, low heats of atomization and high hydration enthalpies, alkali metals lose their valence electron readily and hence are chemically highly reactive.
Their relative tendency to lose electron in chemical reactions depends on upon:
(i) Ionisation enthalpy: Lower the ionisation enthalpy, greater the chemical reactivity.
(ii) Hydration enthalpy: Larger the hydration enthalpy, greater the chemical reactivity.
Now ionisation enthalpies of alkali metals decrease down the group and hence chemical reactivity increases. Also, hydration enthalpies of alkali metals increase down the group and so chemical reactivity increases. Hence, the chemical reactivity increases down the group of alkali metals. Thus, caesium (Cs) is the most reactive among the alkali metals i.e. Cs has maximum tendency to lose the valence electron to form monovalent Cs+ ions.

Some More Questions From The s-Block Elements Chapter

In aqueous solution, Li+ ion has lowest mobility. Why?

Lithium has highest ionisation energy in group 1 elements, yet it is strongest reducing agent. Comment.

The softness of group 1 elements increases down the group with increasing atomic number. Give reason. 

Which is the most reactive alkali metal and why?

Why alkali metals do not form M2+ ions?

Name the radio active element in group 1. How does it resemble with the remaining elements of the group?

Why alkali metals are normally kept in kerosene oil?

Why lithium cannot be stored in kerosene?

Why does lithium form complexes?

Why are alkali metal ions diamagnetic and colourless?

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