Answer
a.
Work Step by Step
The first diagram depicts diatomic molecules of two different elements; therefore, the elements are represented by the two differently colored balls. The red balls are grouped in pairs, and the blue balls are grouped in pairs, meaning that the atoms of each element form diatomic molecules. The two elements are in the gaseous state because they are floating freely in the air.
The second diagram shows the red element has settled into a somewhat rigid arrangement. This means that the mixture of the two elemental gases have been cooled down so that the red element has condensed; however, the blue element is still in gaseous form and is floating freely in the air.
