Sources

Element and nuclear data is compiled from the references below. Where a source sets licence terms, they are stated, and the data drawn from that source remains subject to them.

Some properties are derived rather than taken from a source.

How far the data can be relied on is set out in the Terms of Service.

• NUBASE2020 Half-lives, decay modes and branching ratios, spins and parities, mass excesses, isotopic abundances and discovery years for every known nuclide, and the mass number shown for elements without a standard atomic weight. Cite as F. G. Kondev et al., Chinese Physics C 45, 030001 (2021).
• NIST Atomic Spectra Database Ionization energies, emission line wavelengths and relative intensities, ionization stages, electron configurations, term symbols and level energies. A work of the U.S. government, used with attribution to NIST.
• CODATA recommended values of the fundamental physical constants The values, uncertainties and units of the physical constants, from the 2022 adjustment. Cite as P. J. Mohr, D. B. Newell, B. N. Taylor and E. Tiesinga, Reviews of Modern Physics 97, 025002 (2025), also CC BY 4.0 as arXiv:2409.03787. Published by NIST as Standard Reference Database 121, used with attribution to NIST.
• Crystallography Open Database The Pearson symbols and space groups of the elements and their allotropes. Each form's pair comes from a single COD entry; the structures were determined by the authors those entries cite, R. W. G. Wyckoff's Crystal Structures (1963) among them. CC0 (public domain). Cite as S. Gražulis et al., Journal of Applied Crystallography 42, 726 (2009) and Nucleic Acids Research 40, D420 (2012); many entries come through R. T. Downs and M. Hall-Wallace, American Mineralogist 88, 247 (2003).
• PubChem Melting points, van der Waals radii and electronegativity values, the densities of manganese, barium, praseodymium, iodine and platinum, and an independent check on the atomic masses, densities and boiling points. The formulas and charges of the solubility table's ions and the formulas of their parent acids. Public domain, published by the U.S. National Library of Medicine.
• Lange's Handbook of Chemistry The densities of the solid and liquid elements, their heat capacities, heats of fusion, thermal conductivities and electrical resistivities, the ionic radii and standard electrode potentials of the elements, and the critical points of bromine, chlorine, iodine, mercury, radon and sulfur. The transition ranges and colors of methyl orange and phenolphthalein. Cite as J. A. Dean (ed.), Lange's Handbook of Chemistry, 15th ed. (McGraw-Hill, 1999), Tables 3.2, 4.1, 4.6, 6.3, 6.4, 6.5, 8.23, 8.27 and 8.28.
• Chemistry of the Elements The allotropes of boron, carbon, oxygen, phosphorus, sulfur, selenium, tellurium, polonium, arsenic, antimony, silicon, germanium and tin, and the main phases of the metals, with their structures and densities. The oxidation states of the elements and which of them are common, and who discovered, isolated and named the elements up to fermium, and when. Cite as N. N. Greenwood and A. Earnshaw, Chemistry of the Elements, 2nd ed. (Butterworth-Heinemann, 1997).
• NIST Chemistry WebBook The critical points and densities of hydrogen, helium, nitrogen, oxygen, fluorine, neon, argon, krypton and xenon. Cite as P. J. Linstrom and W. G. Mallard (eds.), NIST Chemistry WebBook, NIST Standard Reference Database 69. Used with attribution to NIST.
• IUPAC Element names, symbols and standard atomic weights, and the group and period numbering.
• Wikipedia Boiling points, heats of vaporization, triple points, electron affinities, magnetic ordering and superconducting temperatures, the empirical, calculated and covalent radii, the abundances in sea water, and Goldschmidt geochemical classes. Also any value the sources above don't give for an element, among them some allotropes, some Pearson symbols and space groups, and some abundances in the Earth's crust and the human body. The transition range and colors of litmus, the colors of universal indicator, and phenolphthalein's return to colorless in strong alkali. CC BY-SA 4.0. The data shown here that is drawn from Wikipedia is shared under the same licence.

• Published melting-curve equations How the melting points of hydrogen, helium, nitrogen, oxygen, neon, argon, krypton and xenon rise with pressure. Datchi et al. (2000), Span et al. (2000), B. A. Younglove, NBS (1982), and Singh et al. (2021); the helium and oxygen constants as transcribed in CoolProp.
• Structure determinations of single phases The structure of ε-cobalt, and the orthorhombic low-temperature phase of dysprosium. Dinega and Bawendi (1999) and Darnell (1963).
• Johnson (2019) The estimated share of each element contributed by each nucleosynthesis process. Cite as J. A. Johnson, Science 363, 474 (2019), table S1.
• Lodders et al. (2025) The abundances of the elements in the Solar System and in meteorites. CC BY 4.0. Cite as K. Lodders, M. Bergemann and H. Palme, Space Science Reviews 221, 23 (2025).
• Asplund et al. (2021) The abundances of the elements in the solar photosphere, as reprinted by Lodders et al. (2025). CC BY 4.0. Cite as M. Asplund, A. M. Amarsi and N. Grevesse, Astronomy & Astrophysics 653, A141 (2021).
• Rudnick and Gao (2003) The abundances of the elements in the Earth's crust, as the composition of the bulk continental crust. Cite as R. L. Rudnick and S. Gao, Composition of the Continental Crust, in Treatise on Geochemistry, Vol. 3 (Elsevier, 2003), Table 9.
• ICRP Publication 23 (1975) The abundances of the elements in the human body, as the content of the 70 kg Reference Man. Cite as International Commission on Radiological Protection, Report of the Task Group on Reference Man, ICRP Publication 23 (Pergamon, 1975), Table 110.
• Discovery and naming reports of IUPAC and IUPAP Who discovered the elements from mendelevium to oganesson, and when, and who proposed the names of seaborgium, hassium, meitnerium and the elements after them. The reports of the Transfermium Working Group (1993) and of the Joint Working Party in 2001, 2003, 2009, 2011 and 2016 (113, 115 and 117, 118), and the IUPAC Recommendations on the names of 1997, 2003, 2004, 2010, 2012 and 2016, all in Pure and Applied Chemistry. The 2016 reports are CC BY-NC-ND 4.0.
• EFSA Dietary Reference Values Which elements are established essential nutrients for humans, and the standing of fluoride and chromium. Cite as European Food Safety Authority, Dietary Reference Values for nutrients: Summary report, EFSA Supporting Publications 2017:e15121 (2017). Reproduction is authorised provided the source is acknowledged.
• Dietary Reference Intakes of the National Academies Which elements are established essential nutrients for humans, among them sodium and chloride. Cite as Institute of Medicine and National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intakes reports (National Academies Press, 1997–2019).
• Maret (2016) Which elements benefit humans without being established as essential, and which ones some microbes need: vanadium, nickel and tungsten. CC BY 4.0. Cite as W. Maret, International Journal of Molecular Sciences 17, 66 (2016).
• Brown et al. (2022) Which elements plants need, among them silicon in rice and horsetail and aluminium in tea, and which ones some bacteria need: sodium, cobalt, vanadium and selenium. CC BY 4.0. Cite as P. H. Brown, F.-J. Zhao and A. Dobermann, Plant and Soil 476, 11–23 (2022).
• ATSDR Toxicological Profiles Which elements are toxic to humans at low doses: beryllium, arsenic, cadmium, antimony, barium, mercury, thallium, lead and uranium. A work of the U.S. government, published by the Agency for Toxic Substances and Disease Registry.