Interesting isotopes
Record holders among more than 3000 nuclides: the longest and widest decay chains, the strangest decays and a few celebrities. Every card leads to the isotope page on Nuclidea - with data, the decay chain and a decay simulator.
Decay chains
The most crowded chain
Iridium-167 (T½ 30 ms) leaves 59 different nuclides behind - none of them from a rare branch, so the whole crowd is on the chart right away.
Open in Nuclidea →The tallest chain
The darmstadtium-267 chain steps down through 29 elements - from darmstadtium (Z = 110) all the way to mercury (Z = 80) - with 98 transitions, more than any other.
Open in Nuclidea →The widest and longest chain
Copernicium-277 decays through nuclides with 33 different neutron numbers, and its longest path to stable lead-207 or thallium-205 is 27 decays in a row.
Open in Nuclidea →Born from the most parents
Lead-208, the end of the thorium series, forms directly from 9 different nuclei. Six of them do it by throwing out a whole light nucleus: carbon-14, oxygen-20, neon-22, neon-24, magnesium-28 or silicon-34.
Open in Nuclidea →Decays
Most decay branches
Argon-31 lives 15 ms and can decay in 7 ways: β⁺, β⁺ followed by one, two or three protons, two protons at once, β⁺ with an alpha particle, and β⁺ with an alpha particle and a proton.
Open in Nuclidea →It throws out neon and magnesium
Uranium-235, the fuel of reactors, besides alpha decay and spontaneous fission can throw out a neon-20, neon-25 or magnesium-28 nucleus. It happens less than once in 10¹¹ decays, but it has been measured.
Open in Nuclidea →The first cluster decay
In 1984 it was noticed that radium-223 sometimes throws out a whole carbon-14 nucleus instead of an alpha particle - roughly once in a billion decays. That is how cluster decay was discovered.
Open in Nuclidea →Most isomers
Besides its ground state, indium-129 has three excited states that live long enough to count as separate isomers - from 98 ms to 1.2 s.
Open in Nuclidea →Two alphas and nothing more
Beryllium-8 forms from as many as 8 different nuclei, but lives only about 8·10⁻¹⁷ s before splitting into two alpha particles. That is why stars have to fuse three helium nuclei almost at once to make carbon.
Open in Nuclidea →Time and nature
The longest half-life ever measured
Tellurium-128 undergoes double beta decay with a half-life of 2.3·10²⁴ years - more than a hundred trillion times the age of the Universe. Yet its product, xenon-128, can be found in tellurium ores.
Open in Nuclidea →The stable one that decays
For decades bismuth-209 was thought to be the heaviest stable nuclide. In 2003 its alpha decay was measured - with a half-life of 2·10¹⁹ years.
Open in Nuclidea →Excited and (almost) eternal
The ground state of tantalum-180 decays in 8 hours, yet its isomer Ta-180m - despite its extra energy - has never been caught decaying. It is the only isomer found in nature as “stable”.
Open in Nuclidea →The heaviest known nuclide
Oganesson-294: 118 protons and 176 neutrons. Only a handful of its atoms have ever been observed, and each decayed in less than a millisecond.
Open in Nuclidea →The closest to us
Potassium-40 (T½ 1.25 billion years) is in bananas, in soil and in us - thousands of its nuclei decay every second in an adult body. 89% of the time it is β⁻ decay, otherwise electron capture or β⁺.
Open in Nuclidea →Elements
Most isotopes
Mercury has 47 known isotopes - from Hg-170 to Hg-216 - more than any other element. Seven of them are stable.
Open in Nuclidea →Most stable isotopes
Tin has 10 stable isotopes - the record of the periodic table. It owes this to its 50 protons: one of the “magic” numbers that make nuclei especially stable.
Open in Nuclidea →Most spectral lines
Iron has 34,825 spectral lines in the NIST ASD database - 70% more than thorium, second on the list. Its lines densely cover the spectra of the Sun and stars.
Open in Nuclidea →Rankings computed on 2026-11-02 from nuclidea.com data: NNDC Wallet Cards 2023 (3118 decay chains from the Nuclidea API, rare branches included) and NIST ASD (spectral lines). “Parents” are nuclei that decay directly into the given nuclide.