Question

Why does the reactivity of alkali metals decrease from cesium to lithium?

a) Decreasing atomic size and increasing ionization energy
b) Increasing atomic size and increasing ionization energy
c) Decreasing atomic size and decreasing ionization energy
d) Increasing atomic size and decreasing ionization energy

Answer 1

The reactivity of alkali metals decreases from cesium to lithium because of increasing atomic size and decreasing ionization energy, with cesium having the lowest ionization energy making it the most reactive. option (B)

Step-by-step explanation:

The reactivity of alkali metals decreases from cesium to lithium due to increasing atomic size and decreasing ionization energy. As we move down the group in the periodic table, atomic size increases due to the addition of shells.

This places the outer electron further from the nucleus, weakening the electrostatic attraction and thus making it easier to lose the valence electron. Simultaneously, the ionization energy, which is the energy required to remove this electron, decreases. Therefore, the correct answer is (d) Increasing atomic size and decreasing ionization energy.