Hydrogen (1H) has three naturally occurring isotopes: 1H, 2H, and 3H. 1H and 2H are stable, while 3H has a half-life of 12.32 years. Heavier isotopes also exist; all are synthetic and have a half-life of less than 1 zeptosecond (10−21 s).
Hydrogen is the only element whose isotopes have different names that remain in common use today: 2H is deuterium and 3H is tritium. The symbols D and T are sometimes used for deuterium and tritium; IUPAC (International Union of Pure and Applied Chemistry) accepts said symbols, but recommends the standard isotopic symbols 2H and 3H, to avoid confusion in alphabetic sorting of chemical formulas. 1H, with no neutrons, may be called protium to disambiguate. During the early study of radioactivity, some other heavy radioisotopes were given names, but such names are rarely used today.
List of isotopes
Nuclide
Z
N
Isotopic mass
Discovery year
Half-life
Decay mode
Daughter isotope
Spin and parity
Natural abundance (mole fraction)
Normal proportion
Range of variation
H
1
0
1.007825031898(14)
1918
Stable
1/2+
H
1
1
2.014101777844(15)
1932
Stable
1+
H
1
2
3.016049281320(81)
1934
12.32(2) y
β
He
1/2+
trace
H
1
3
4.02643(11)
1981
139(10)×10 s
n
H
2−
H
1
4
5.03531(10)
2001
86(6)×10 s
2n
H
(1/2+)
H
1
5
6.04496(27)
1984
294(67)×10 s
2−#
H
1
6
7.052750(108)#
2003
652(558)×10 s
1/2+#
This table header & footer:
Modes of decay:
n:
Neutron emission
Hydrogen-1 (protium)
H consists of 1 proton and 1 electron: the only stable nuclide with no neutrons (see diproton for a discussion of why no others exist).
H (atomic mass 1.007825031898(14) Da) is the most common hydrogen isotope, with an abundance of > 99.98%. Its nucleus consists of only a single proton, so it has the formal name protium.
The proton has never been observed to decay, so H is considered stable. It...
