Question

All the elements of Group IIA are less reactive than alkali metals. This is because these elements have

a) Lower atomic numbers and smaller atomic radii.

b) Higher atomic numbers and larger atomic radii.

c) Similar electronegativity values.

d) Increased valence electrons in their outer shells.

Answer 1

Group IIA elements, or alkaline earth metals, are less reactive than alkali metals mainly due to their higher ionization energies which come from having an increased number of valence electrons in their outer shells.

Step-by-step explanation:

The elements of Group IIA, known as the alkaline earth metals, are less reactive than the alkali metals because the atoms of the alkaline earth metals have a higher nuclear charge, which results in smaller atomic radii and higher first ionization energies compared to the alkali metals within the same period.

These characteristics make the alkaline earth metals less willing to lose their valence electrons, thus being less reactive. However, they're still highly reactive, just not as much as the alkali metals that more readily lose their single valence electron due to lower ionization energies.

In conclusion, the correct answer to why Group IIA elements are less reactive than alkali metals is d) Increased valence electrons in their outer shells. This increased number results in higher ionization energies and thus lower reactivity compared to Group I elements.