# Does hydrogen really have seven isotopes?

I know that there are 3 isotopes of Hydrogen. But according to this website it is showing 7 http://periodictable.com/Properties/A/KnownIsotopes.htmlWebsite

• As you can see by your link, heavier isotopes have decay time measured in $10^{-13}$ fractions of nanosecond. They are of theoretical interest for nuclear physics, but from chemists point of view can be ignored completely. Feb 25 '15 at 16:53
• Look at the data there. The half-life of 3H is 12 years. The half-life of 4H is 1.39×10-13 nanoseconds. Does that count as existence for you? Feb 25 '15 at 16:53

Yes, there are seven known isotopes of hydrogen, though only two ($$\ce{^1H}$$ and $$\ce{^2H}$$) are stable with respect to nuclear decay, and only three ($$\ce{^1H}$$, $$\ce{^2H}$$ and $$\ce{^3H}$$) exist/can be made in enough quantities to be relevant outside of nuclear physics. All other hydrogen isotopes have extremely small half-lives. The next most stable hydrogen isotope after $$\ce{^3H}$$ ($$t_{1/2}=12.3\ yr$$) seems to be $$\ce{^5H}$$ ($$t_{1/2} \sim 10^{-21}\ s$$). Given that even the fastest chemical reactions happen in timespans of the order of $$10^{-15}\ s$$, we can safely discard any influence of hydrogen isotopes heavier than $$\ce{^3H}$$ in chemistry.