Elements are arranged in the periodic table in order of increasing atomic number. For example hydrogen has the atomic number of one, helium two, lithium three etc. The first energy level (the one ...

An element's atomic number defines it ... There are three isotopes of hydrogen: hydrogen, deuterium (hydrogen-2) and tritium (hydrogen-3): Carbon has three isotopes: \(_{6}^{ ...

Heavy water is a form of water with a unique atomic structure and properties coveted ... H 2 0—each molecule of heavy water contains two hydrogen atoms and one oxygen atom.