Isotopes of the chemical elements
Every isotope of elements 1–118 listed by NIST, with its relative atomic mass (the mass of one atom in daltons), its natural abundance where it occurs in nature, and its element's standard atomic weight. One row per isotope.
Columns
Stable keys — use them in the API, SQL and code
| Key | Name | Type | Description |
|---|---|---|---|
| isotope | Isotope | string | Element symbol and mass number, e.g. C-14. |
| atomic_number | Atomic number (Z) | integer | Number of protons. |
| element_symbol | Element | string | — |
| nist_symbol | NIST symbol | string | Symbol as printed by NIST (D and T for deuterium and tritium). |
| mass_number | Mass number (A) | integer | Protons plus neutrons. |
| neutrons | Neutrons (N) | integer | Mass number minus atomic number. |
| relative_atomic_mass | Relative atomic mass | number · Da | Mass of one atom relative to 1/12 of a carbon-12 atom (daltons, u). |
| relative_atomic_mass_uncertainty | Mass uncertainty | number · Da | — |
| mass_estimated | Mass estimated | boolean | True when NIST marks the mass as estimated from systematics rather than measured. |
| natural_abundance | Natural abundance | number | Mole fraction (0–1) of the element's atoms that are this isotope in nature; blank for isotopes not found in nature. |
| natural_abundance_uncertainty | Abundance uncertainty | number | — |
| naturally_occurring | Occurs in nature | boolean | True when NIST gives a natural isotopic composition. |
| standard_atomic_weight | Standard atomic weight (element) | string | The element's standard atomic weight as published by NIST: value(uncertainty), [low,high] interval, or [mass number] for elements with no stable isotopes. |
| notes | Notes | string | NIST footnotes for the element: g, m, r. |
More in Chemistry & Materials
Periodic table of the elements
All 118 chemical elements with atomic mass, electron configuration, electronegativity, melting and boiling points, density and year of discovery. One row per element.
Energy levels of neutral atoms: gallium onward (Z 31+)
Energy levels of neutral atoms of the elements from gallium onward (atomic number 31 and up), from the NIST Atomic Spectra Database: each level's electron configuration, term, total angular momentum J and energy above the ground state. One row per level (plus the ionization limits NIST lists).
Energy levels of neutral atoms: hydrogen to zinc (Z 1–30)
Energy levels of neutral atoms of the elements hydrogen through zinc (atomic numbers 1–30), from the NIST Atomic Spectra Database: each level's electron configuration, term, total angular momentum J and energy above the ground state. One row per level (plus the ionization limits NIST lists).
Strong spectral lines of the elements
The strongest emission lines of 99 elements, from hydrogen to einsteinium, as tabulated in NIST's Handbook of Basic Atomic Spectroscopic Data. One row per spectral line: element, ion stage, wavelength, relative intensity and whether it is a persistent line.
Mineral species
Mineral species recorded in Wikidata — from quartz and diamond to rare species known from a single locality — with chemical formula, crystal system, Mohs hardness, density and IMA mineral symbol. One row per mineral species.
Ionization energies of the elements (all ion stages)
The energy needed to remove each successive electron from an atom or ion, for every ionization stage of elements 1–110, from the NIST Atomic Spectra Database. One row per ion: e.g. Fe I (neutral iron, first ionization energy) through Fe XXVI.