Question

Explain why hydrogen and oxygen are considered elements whereas water is not considered an element.

Answer 1

hydrogen and oxygen are made up of same kind of atom hence it is considered as elements whereas water is made by the combination of different kinds of atoms  hence it is called as a compound...

Answer 2

An element is the smallest unit of any substance that show identical properties and is composed of same type of atoms. Since, hydrogen and oxygen has only either hydrogen or oxygen atoms, therefore, they are considered as elements.

On the contrary, compounds comprise "more than one element". Here, the elements are bonded with the chemical bond, hence, water is considered as compound as it is composed of "two hydrogen atoms" and "one oxygen atom".