Isotopes

thumb|300px|The three naturally occurring isotopes of hydrogen. The fact that each nuclide has 1 proton makes them all isotopes of [[hydrogen: the identity of the isotope is given by the number of protons and neutrons. From left to right, the isotopes are protium (H) with 0 neutrons, deuterium (H) with 1 neutron, and tritium (H) with 2 neutrons.]]

thumb|Chart of known nuclides . The vast majority are radionuclides.

Nuclides (or nucleides, from nucleus; also known as nuclear species) are a class of atoms characterized by their number of protons, Z, their number of neutrons, N, and their nuclear energy state.

relative proportion of an isotope as found in nature; abundance of isotopes of a chemical element as naturally found on a planet

number of protons or neutrons that make a nucleus particularly stable

region of the chart of the nuclides containing isotopes of super-heavy elements theorized to be much more stable than others

nucleus of this isotope does not undergo radioactive decay

nuclides predating the Earth's formation (found on Earth)

200px|thumbnail|right| A carbon-11 labelled radiopharmaceuticalRadiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which is different from contrast media which absorb or alter external electromagnetism or ultrasound. Radiopharmacology is the branch of pharmacology that specializes in these agents.

technique to follow reactions by using atomic isotopes

one of the 22 chemical elements that is found naturally on Earth essentially as a single nuclide (which may, or may not, be a stable nuclide)

In chemistry, isotopologues (also spelled isotopologs) are molecules that differ only in their isotopic composition. They have the same chemical formula and bonding arrangement of atoms, but at least one atom has a different number of neutrons than the parent.

characteristic set of ratios of stable or unstable isotopes

analytical technique

one of 26 chemical elements which have only a single stable isotope (nuclide)

water with a lower concentration of deuterium than occurs naturally

ratio of two stable isotopes

region of the chart of the nuclides in which bound nuclei are possible

Water made of uncommon hydrogen and oxygen isotopes