How do the alkali metals differ from the alkaline earth metals?

Answer & Explanation:

The alkali metals are the elements found in the first group of the periodic table.Alkaline earth metals are found in the second group of the periodic table. Alkali metals are Lithium (Li), sodium(Na), potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr).Alkaline earth metals include; Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and Radium (Ra).Alkali metals are very reactive and none of these metals do not occur as free metals in nature.Alkaline metals are also do not occur freely in nature and they are also very reactive.For alkali elements, the densities of Lithium and Sodium are less than the density of water. However, the other elements are denser than water. Many of alkali metal compounds (NaCl, KCl, Na2, CO3, NaOH) are commercially very important.Alkaline elements in this group are denser than water.

Density= mass/volume so 5.1 divided by 4.7 is  5.1 / 4.7 =1.08510638298round to the correct number of sig figs