WebElements Periodic Table of the Elements | Periodicity | Atomic number | periodicity

	Atomic number Units None The atomic number corresponds to the number of protons in the nucleus of an atom of that element. It also corresponds to the number of electrons in the neutral atom. Notes None Literature sources International Union of Pure & Applied Chemistry: Commission on the Nomeclature of Inorganic Chemistry, Nomenclature of Inorganic Chemistry Recommendations 1990, Ed. G.J. Leigh, Blackwell Science, Oxford, 1990. Pure Appl. Chem., 1994, 66, 2423. WebElements Shop WebElements now has an online chemistry shop at which you can buy periodic table posters, mugs, T-shirts, games, molecular models, and more.
Periodicity Cityscape Cylinders Line graph Bar chart Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Group 9 Group 10 Group 11 Group 12 Group 13 Group 14 Group 15 Group 16 Group 17 Group 18 Period 2 Period 3 Period 4sp Period 4 Period 4d Period 5sp Period 5spd Period 5d Period 6sp Period 6spd Period 6 Period 6d Period 6f Period 7sp Period 7spd Period 7 Period 7d Period 7f s- and p-Block d-Block f-Block		Search WebElements Search Chemistry Web Custom Search Essential data Essential data: name, symbol, atomic number, and atomic weight; block, period, group number, and group name in periodic table; description; standard state; registry number; and isolation History: meaning of name; discovery; and history of the element Find a property The elements round us Uses Geology: Abundance of elements in the universe; the sun; meteorites; Earth's crust; oceans; and streams Biology: abundance in humans; biological role; and health hazards Compounds Compounds: halides, oxides, sulfides, hydrides, and complexes; lattice energies; and reduction potentials Reactions of : reactions with air; water; halogens; acids; and bases Electronegativities: Pauling; Sanderson; Allred-Rochow; Mulliken-Jaffe; and Allen Bond enthalpies of diatomic species Lattice energies: oxides and halides Element properties Physics properties: boiling point; melting point; density; and molar volume; thermal conductivity; and electrical resistivity; bulk modulus; critical temperature; superconductivity temperature; hardness (mineralogical, Brinell, and Vickers); linear expansion coefficient; Poisson's ratio; reflectivity; refractive index; rigidity modulus; Young's modulus; and velocity of sound Images Allotropes Crystal structure Thermochemistry: enthalpies of atomisation, fusion, and vaporisation, thermodynamic properties Atom properties Electronic properties: electronic configuration; term symbol; electron affinity; ionisation energies; and atomic spectra Atom sizes: atomic radii; Shannon and Pauling Ionic radii; covalent radius; metallic radius; element bond length; and Van der Waals radius Electron shell properties: effective nuclear charge; electron binding energies; and valence orbital radii maxima Nuclear properties Isotopes: isotope abundances; radioactive isotopes; isotope masses; nuclear spins; and nuclear magnetic moments NMR properties: frequencies; NMR isotopes; magnetogyric ratios; quadrupole moments; receptivities; and relative sensitivities