Question

Alkali metals are not found in free state due to their highly reactive nature.This is due to :

• A. their large size and low ionisation enthalpy
• B. their large size and high ionisation enthalpy
• C. their low ionisation enthalpy and high electron gain enthalpy
• D. their tendency to impart colour to the flame.

Answer 1

Answer: (A)

their large size and low ionisation enthalpy

Their reactivity depends on how easily the element can lose their electron to achieve the nearest noble gas configuration. All the alkali metals have one valence electron $n{s}^1$ . outside the noble gas core. The loosely held s-electron in the outermost valence shell of these elements makes them the most electropositive metals. They readily lose electron to give monovalent $M^{+}$ ions. As the atomic size increases, the no. of shells increases so the force of attraction between the nucleus and the electron of the valence shell decreases, so they can easily lose electron upon irradiation to heat and light, so they have low ionization enthalpy. Therefore, alkali metals are not found in the free state, they are commonly found as metal oxides, metal carbonates etc.