An element is a pure substance that cannot be chemically split or decomposed to form other substances. Oxygen is an element. Hydrogen is an element. There are over 100 other elements. Water is not an element.
Water is a compound composed of the elements oxygen and hydrogen, chemically joined.
Everything on the earth is composed, or made up, of one or more elements. There are just over 100 different elements known at this time. The Periodic Table is a list of all of the known elements. They are arranged in a table according to characteristics or properties that they have in common. Metals are placed on the left side of the Periodic Table.