The atmosphere is comprised of gases which are considered to be permanent (gases which remain essentially constant by percent) and gases considered to be variable (gases which have changing concentrations over a finite period of time).he atmosphere is comprised of gases which are considered to be permanent (gases which remain essentially constant by percent) and gases considered to be variable (gases which have changing concentrations over a finite period of time).
, also known as heavy hydrogen) is one of two stable isotopes of hydrogen. The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen isotope, protium, has no neutron in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom in 7003642000000000000â 6420 of hydrogen.
Ordinarily, the nucleus of a hydrogen atom consists of a single proton, but deuterium is an isotope of hydrogen that contains one neutron as well as one proton, vastly increasing the weight of the element and altering its atomic properties.Heavy water reactors offer some advantages over those that use normal, or light, water as a neutron moderator.