Earth (chemistry)

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The term earths was historically applied to certain substances that were once thought to be elements, and this name was borrowed from one of the four classical elements of Plato[citation needed] the other three being air, water, and fire. "Earths" were later found to be metallic oxides,[1] and the corresponding metals were classified into the corresponding groups; rare earth metals and alkaline earth metals.[citation needed]


  1. ^ "Alkaline-earth metal". Encyclopædia Britannica. Retrieved 18 April 2019. By the early 1800s it became clear that the earths, formerly considered to be elements, were oxides, compounds of a metal and oxygen.