Chapter 21, Problem 29PS

Interpretation Introduction

Interpretation: The reaction of sodium with halogens is to be stated and two physical properties of alkali metal halides is to be predicted.

Concept introduction: Alkali metals belong to group $\text{1A}$ of the periodic table. It consists of elements lithium, sodium, potassium, rubidium, cesium and francium. All of them have one electron in their outermost shell. They are all metals and tend to lose their valence electron. Thus, they have $+1$ oxidation number.

Halogens belong to group $\text{7A}$ of the periodic table. It consists of elements fluorine, chlorine, bromine and iodine. The symbol $\text{X}$ is used for halogens. They have five valence electrons in the outermost shell and gain one electron to attain noble gas configuration. The oxidation number of halides is $-1$.

Alkali metals are very reactive and form compounds with chlorides, oxides and water. Alkali metals combine with halogens and there is a transfer of electrons from the metal to halogens and thus ions are formed where metal has a positive charge and halogens are negatively charged. Thus, alkali metals react vigorously with halogens to form alkali metal halides.