Start Cosmogenic radionuclide dating

Cosmogenic radionuclide dating

Curie · Skłodowska-Curie · Davisson · Fermi · Hahn · Jensen · Lawrence · Mayer · Meitner · Oliphant · Oppenheimer · Proca · Purcell · Rabi · Rutherford · Soddy · Strassmann · Szilárd · Teller · Thomson · Walton · Wigner The three naturally-occurring isotopes of hydrogen.

However, because isotope is the older term, it is better known than nuclide, and is still sometimes used in contexts where nuclide might be more appropriate, such as nuclear technology and nuclear medicine.

Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons.

The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.

Thomson eventually concluded that some of the atoms in the neon gas were of higher mass than the rest. In 1919 Aston studied neon with sufficient resolution to show that the two isotopic masses are very close to the integers 20 and 22, and that neither is equal to the known molar mass (20.2) of neon gas.

This is an example of Aston's whole number rule for isotopic masses, which states that large deviations of elemental molar masses from integers are primarily due to the fact that the element is a mixture of isotopes.

In most cases, for obvious reasons, if an element has stable isotopes, those isotopes predominate in the elemental abundance found on Earth and in the Solar System.

However, in the cases of three elements (tellurium, indium, and rhenium) the most abundant isotope found in nature is actually one (or two) extremely long-lived radioisotope(s) of the element, despite these elements having one or more stable isotopes.

From left to right, the isotopes are protium ( Isotopes are variants of a particular chemical element which differ in neutron number.