Hydrogen is a chemical element that is found abundantly in nature. It is one of the main constituents of water. The atomic number of hydrogen is 1, and its atomic weight is 1.00794. Atoms of the same element with different number of neutrons are known as isotopes. Mostly, all elements found in nature have different isotopes. They have similar chemical properties of the element, but differ in their physical properties.
There are three isotopes of hydrogen that are naturally occurring―protium, deuterium, and tritium.
Hydrogen - 1
Hydrogen - 1 or protium, is also written as 1H. This isotope is abundantly found in nature. It consists of 1 proton and no neutrons.
Hydrogen - 2
Hydrogen - 2 or deuterium, is also written as 2H, and 'D' is also used as a symbol for deuterium. It contains one proton and one neutron in the nucleus. Deuterium is not a radioactive molecule. When 2H is added to water molecules, it is called heavy water. This water is used as a neutron moderator, and coolant for nuclear reactors.
Hydrogen - 3
Hydrogen - 3 is also known as tritium, that contains 1 proton and 2 neutrons in the nucleus. It is also written as 3H, and sometimes symbolically referred as 'T'. This is one of the radioactive isotopes of hydrogen, that decays into helium -3 through β− decay, and has a half-life of 12.32 years. It was commonly used as a radiolabel in chemical and biological experiments. It is also used as a thermonuclear fusion weapon, and a tracer in isotope geochemistry.
Hydrogen - 4
Hydrogen - 4 or 4H, is one of the most unstable isotopes of hydrogen. It contains 1 proton and 3 neutrons in the nucleus. It does not occur naturally, and is synthesized by bombardment of tritium and fast-moving deuterium nuclei. It is also called quadrium.
Hydrogen - 5
Hydrogen - 5 or 5H, is another unstable isotope. This isotope also is synthesized by the bombardment of tritium with fast-moving tritium nuclei. It contains a proton and 4 neutrons in the nucleus.
Hydrogen 6 or 6H, has 1 proton and 5 neutrons. This isotope decays through triple neutron emission, and has a half-life of 3 x 10 -22 seconds.
Hydrogen - 7
Hydrogen - 7 or 7H, contains 1 proton and 6 neutrons.
These are the isotopes of hydrogen, of which, only three are naturally occurring. Protium and deuterium are the stable isotopes,. whereas, 3H, 4H, 5H, 6H, and 7H are the radioactive isotopes.