Electronegativity and ionization. Pauling electronegativity from standard reference tables (CRC Handbook); lead is given for lead(II), 1.87, where some tables list 2.33 for lead(IV). First ionization energies from the NIST Atomic Spectra Database, rounded to whole kJ/mol. For elements 104 to 118 they are theoretical predictions (shown dashed).
Melting and boiling. At normal air pressure, mostly CRC Handbook values as tabulated in Wikipedia's List of chemical elements and element pages. Carbon and arsenic sublime instead of melting. Values marked estimated (francium, astatine, actinium, einsteinium and heavier) are predictions or uncertain, and several actinide boiling points are extrapolated.
Masses and nuclei. Atomic masses are IUPAC standard atomic weights; masses in [brackets] are the mass number of the longest-lived isotope. Neutron counts refer to the most common (or longest-lived) isotope.
Discovery. Years and discoverers follow Wikipedia's Timeline of chemical element discoveries (year of first observation; isolation listed separately).
Abundance. Earth's crust: CRC Handbook, 97th edition, as tabulated in Wikipedia's Abundance of elements in Earth's crust; values below about 1 ppb are estimates and vary by orders of magnitude from place to place. Seawater: the same CRC table (95th edition), with indium taken from modern measurements. Universe: the Sun's composition from Asplund, Amarsi and Grevesse (2021). Full references are listed in the Abundance view.
Magnetism. Unpaired-electron counts for the free atom follow Hund's rule on the ground-state configuration, and the 7p½/7p³⁄₂ split for elements 113 to 118. Magnetic types at room temperature are from Wolfram ElementData (via periodictable.com); fluorine and radon are inferred from their closed shells, and tin refers to white tin. Curie and Néel temperatures follow Kittel's Introduction to Solid State Physics and standard references. Neodymium magnets: Sagawa et al. and Croat et al. (1984), Herbst (1991); full references are listed in the Magnetism view.
Half-life. Half-lives from NUBASE2020 (Kondev et al., 2021) via the mendeleev database; for elements 104 to 118 they rest on a few atoms each. Binding and reaction energies are computed from isotope masses. Fission yields, reactor, waste and fusion figures are referenced in the Half-life view (checked October 2026).
Beyond 118. Period-8 predictions follow Fricke, Greiner and Waber (1971) and Pyykkö (2011); predicted properties of elements 119 and 120 are as collected in Wikipedia (October 2026). None of these elements has been made yet. The 5g pictures are hydrogen-like orbitals, drawn for shape only. Full references are listed in the Beyond 118 view.
Oxidation states. The common and other states in the English Wikipedia element infoboxes (checked October 2026); for elements 104 to 118 only the states marked as observed there are treated as known, and the rest as predictions. For the noble gases, 0 (the free gas, how nearly all their atoms exist) is shown as the common state.