Re: Why is earth, fire water, and air not part of the elements?

Earth, fire, water, and air are called classical elements and derive from the ancient Greek philosophers (Chinese, Indian and Japanese as well) and were used in alchemy and other pseudosciences. Plato mentions these elements adopting a list created by the Sicilian philosopher Empedocles (ca. 450 BC). Empedocles called these the four "roots"; Plato seems to have been the first to use the term "element (stoicheion)" in reference to air, fire, earth, and water. According to Aristotle:

Air is primarily wet and secondarily hot.
Fire is primarily hot and secondarily dry.
Earth is primarily dry and secondarily cold.
Water is primarily cold and secondarily wet.

These all describe a state of matter.

However, in modern science were refer to chemical elements which are defined by unique atomic identity (atomic number) from the number of protons in the nucleus of the atom. The classical elements refer to mixtures of chemical elements combined as molecules or combinations of molecules for the most part (air, water, earth) but more importantly were used as a way to describe things that appeared in nature. Chemical elements also describe things that appear in nature but at much smaller scale. They are used to describe the fundamental building blocks of nature, the molecule. As such the classical elements do not belong in the category of a chemical element, because they describe large-scale molecular phenomena and not atomic phenomena.