The most common isotope of this element is called protium because its nucleus is only one proton

Isotope 90 of this element atomic number 38 is a dangerous product of nuclear fallout

In 2006 the 210 isotope of this was slipped into the tea of ex-KGB man Alexander Litvinenko with deadly results

99% of all carbon on earth is this isotope not 14

The 60 isotope of this element has replaced radium in cancer treatment because it's safer

Unstable thorium-230 breaks down into the 226 isotope of this Curie-ous element

In 1960 the wavelength of light from krypton-86 was used to define this measurement also 39.37

Isotopes are 2 forms of an element with the same number of protons but different numbers of these particles

As in planetary sequence neptunium-239 emits a beta particle & becomes isotope 239 of this element

The hydrogen isotope called this was discovered in 1932 2 years before tritium