Chapter EH, Problem 7R

Solution

Interpretation: To determine the trend in the density of the alkali metals as the atomic number increases.

Concept Introduction: Atomic number can be known as the count of protons that are present in the nucleus of a particular atom. It can be said that the atomic number will be equal to the count of protons.

When the atomic number increases the density of alkali metals increases. On moving down the group alkali metal density increases $\text{Li to Cs}$ .

When the atomic number increases then the atomic radius also increases. Density is mass divided by volume. The volume and mass both increase with the atomic radius. Density increases down the group because the increase in mass is more than that of the increase in volume with the increase in atomic number.

The trend of the density of alkali metals is $\text{Li}\text{<}\text{Na}\text{<}\text{K<}\text{Rb}\text{<}\text{Cs}$ .