E is the most dense while
A is the least dense

Density is a helpful property.  For example galena, a mineral of lead sulfide (PbS) is very dense.  A geologist learns to “heft’ a stone to “feel” the density. Precise measurement of the density of a pure substance will aid in the identification of the substance.  Density equals the mass of an object divided by the volume of that object, measured in grams per cubic centimeters (D=M/V). 

The masses of atoms and the spacing between the atoms, determine the density of a material.  We think of density as the lightness or heaviness of materials.  It is a measure of the "compactness" of matter.  The density of lead is greater than that of ice, and that of ice is less than water. Because the density of ice is less than water, ice floats.  Gold is very dense. Panning for gold uses this property to gold so the flakes of gold settle out of the water.