Why are hydrogen and oxygen called elements?

Answer 1

They are called elements because they are each pure.. Hydrogen is an element because it's only made up of hydrogen atoms and the same with oxygen.. however with something like CO2 (carbon dioxide) That is made up of 2 elements, (Carbon and Oxygen)- so this would not be called an element. Everything that you see in the periodic table is an element

Answer 2

The most common isotope of hydrogen (protium) has no neutrons, just one proton and one electron. It is unique because all other elements have at least one neutron (not counting unstable isotopes).

Answer 3

Because it is a pure substance i.e. it is not made up of different chemicals.