Chapter 18, Problem 1E

How do alkali metals differ from alkaline each metals in atomic structure and general properties?

Interpretation Introduction

Interpretation:

The differences between alkali and alkaline earth metals in terms of their atomic structure and properties needs to be explained.

Concept Introduction:

• The alkali and alkaline earth metals are referred as the ‘s-block’ elements and belong to Group IA and IIA respectively in the periodic table
• Atomic structure of an element depicts the arrangement of electrons around the nucleus of an atom
• Variations in the physical and chemical properties across elements present in the periodic table can be explained on the basis of their atomic structure.

Answer to Problem 1E

The main difference between the alkali and alkaline earth metals lies in their electron configuration with the former having one valence electron while the latter having two. It is this difference which brings about variations in their properties.

Explanation of Solution

The alkali earth metal include: Li, Na, K, Rb, Cs and Fr. They have a valence electronic configuration which can be generally represented as ns¹, where ‘n’ is the principle quantum number.

The alkaline earth metals include: Be, Mg, Ca, Sr, Ba and Ra. In contrast to alkali metals they have a fully filled outer s-orbital with a valence configuration represented as ns².

Here are some of the key differences between the two groups

1. Alkali metals have one electron in their outermost shell whereas, alkaline earth metals have two electrons
2. Alkali metals form cations with a charge of +1 unlike +2 cations in the case of alkaline earth metals
3. Alkali metals are more reactive than the alkaline series
4. Alkali metals tend to be softer and can be cut with a sharp knife. While alkaline metals are harder and form stronger metallic bonds