Hydrogen (H) is a very special type of atom.

He weighs so little that he "circulates"� freely in space. His family consists of:
Hydrogen H1 with one proton in it's nuclear core: This sort thus is simple, stable hydrogen.
Hydrogen H2 with a proton and a neutron its nuclear core: It is stable as well, but weighs double compared to its "brother". He carries a very special name: Deuterium.

But we also know heavy water, which consists of 2 hydrogen and 1 oxygen atom. Heavy water has a speciality: The hydrogen-atoms weigh double again - so heavy water contains the "heavy brothers of the family" the atoms of Deuterium.

Hydrogen H3 has 1 proton an 2 neutrons in its core. This is the most aggressive member of the whole family, called Tritium. It can be very dangerous and most aggressive, because it is not stable - it is instable. The atoms of Tritium decay into other particles. By that Tritium sends rays into the atmosphere, which damage the health of everything living. The rays are so strong that they can even destroy our cells completely by intruding into each cell.

� our body, which is built by millions of cells, needs every cell to be healthy and strong.