Chemical element

A chemical element is a material consisting of one type of atom, such as hydrogen, oxygen, or iron. There are over two hundred naturally-occurring elements, and many more that are synthesized. Earth scientists had only discovered 92 naturally-occurring elements as of the year 2152. There are over 323 elements in all. Elements occur in five different states: solid, liquid, gas, plasma, or a Bose-Einstein condensate. Elements can also exist, composed of antiparticles, as antimatter. 

The preindustrial civilization of Barkon IV incorrectly believed that the basic elements of the universe were sky, fire, rock, and water, and these elements were found in everything in existence.