Question

Choose the correct order of density of the alkali metals.

• A. Li < K < Na < Rb < Cs
• B. Li < Na < K < Rb < Cs
• C. Cs < Rb < K < Na < Li
• D. Li < Na < K < Cs < Rb

Answer 1

The Correct Option is A

 The question asks for the order of density of alkali metals. Alkali metals are located in Group 1 of the periodic table. The density of alkali metals generally increases as we move down the group. However, the density order is not perfectly linear due to differences in atomic structure, particularly due to the way atoms pack in the crystalline solid form.

Let's analyze the options given:

Li < K < Na < Rb < Cs

This is the correct order of density for alkali metals. Even though potassium (K) comes after sodium (Na) in the periodic table, sodium is denser than potassium due to its closer atomic packing.

Li < Na < K < Rb < Cs

This is incorrect because potassium (K) is less dense than sodium (Na), which contradicts empirical density measurements.

Cs < Rb < K < Na < Li

This order is incorrect because cesium (Cs) and rubidium (Rb) are among the densest of the alkali metals, and would not appear first in a list ordered by increasing density.

Li < Na < K < Cs < Rb

The order incorrectly places cesium (Cs) before rubidium (Rb), whereas rubidium is denser than cesium.

Therefore, the correct order of density is Li < K < Na < Rb < Cs.