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Isotopes of Hydrogen
Notes
Hydrogen is the only element that has different names for its isotopes in common use today.
The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, but the corresponding symbol P is already in use for phosphorus and thus is not available for protium.
Notable Isotopes show graph
1H (Protium) [0 neutrons]
Abundance: 99.985%
Stable with 0 neutrons
Because the nucleus of this isotope consists of only a single proton, it is given the descriptive but rarely used formal name protium.
2H (Deuterium) [1 neutrons]
Abundance: 0.0145%
Stable with 1 neutron
Essentially all deuterium in the universe is thought to have been produced at the time of the Big Bang, and has endured since that time. Deuterium is not radioactive, and does not represent a significant toxicity hazard. Water enriched in molecules that include deuterium instead of normal hydrogen is called heavy water.
Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for 1H-NMR spectroscopy.
3H (Tritium) [2 neutrons]
Abundance: trace
Half life: 12.32 years [ beta- ]
Decay Energy: 0.019 MeV
Decays to 3He.
Small amounts of tritium occur naturally because of the interaction of cosmic rays with atmospheric gases; tritium has also been released during nuclear weapons tests.
It is used in nuclear fusion reactions, as a tracer in isotope geochemistry, and specialized in self-powered lighting devices. It has also been used in chemical and biological labeling experiments as a radiolabel.
4H (tetranium/quadium) [3 neutrons]
Abundance: 
Half life: 1.39(10) x 10-22 seconds
Hydrogen-4 is highly unstable. The nucleus consists of a proton and three neutrons. It has been synthesised in the laboratory by bombarding tritium with fast-moving deuterium nuclei.
5H (Pentium) [4 neutrons]
Abundance: Highly unstable
Half life: 10-21 seconds (?)
Hydrogen-5 is highly unstable. The nucleus consists of a proton and four neutrons. It has been synthesised in the laboratory by bombarding tritium with fast-moving tritium nuclei. In this experiment, the one tritium nucleus captures two neutrons from the other, becoming a nucleus with one proton and four neutrons.
6H (Hexium) [5 neutrons]
Abundance: 
Half life: 2.90(70) x 10-22 seconds
Hydrogen-6 decays through triple neutron emission.
7H (Septium) [6 neutrons]
Abundance: 
Half life: 2.3 x 10-23 seconds
Hydrogen-7 consists of a proton and six neutrons. It was first synthesised in 2003 by a group of Russian, Japanese and French scientists at RIKEN's RI Beam Science Laboratory by bombarding hydrogen with helium-8 atoms. In the resulting reaction, the helium-8's neutrons were donated to the hydrogen's nucleus.