Browse all 118 elements in an interactive periodic table: click an element to see its IUPAC standard atomic mass, its full and abbreviated electron configuration with the orbital diagram, its group, period, block and category, the first ionization energy and the melting point. Color the table by category, block, state or with a heat map of each property to see the periodic trends.
The first ionization energy is the one in the NIST periodic table (SP 966) and, for elements not listed there, the one in Wikidata. Atomic masses, melting points and names from Wikidata, public-domain data (CC0 1.0), checked one by one by Simuveliq. Atomic masses are the IUPAC standard ones. The other values on each card state their own source.
The periodic table orders the 118 known elements by their atomic number Z, the number of protons in the nucleus. Its shape is not arbitrary: it reflects how electron orbitals fill up, which is why elements in the same column have similar chemical properties. This guide explains how to read it and what trends show up when you color it.
The standard atomic weight is the average of the masses of an element's isotopes, weighted by their natural abundance; that is why it is almost never a whole number (chlorine, with its isotopes 35 and 37, is about 35.45). The table uses the IUPAC standard atomic weights. For elements without a characteristic isotopic composition, such as those with no stable isotopes, the mass number of the most stable isotope is shown in brackets.
Electrons fill orbitals in order of increasing energy, which approximately follows the Madelung rule (increasing n + ℓ; for equal n + ℓ, lower n first):
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p
Example, iron (Z = 26): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶, abbreviated with the previous noble gas as [Ar] 3d⁶ 4s². The superscripts add up to 26, the number of electrons. There are well-known exceptions where a half-filled or filled d subshell is more stable: chromium is [Ar] 3d⁵ 4s¹ and copper [Ar] 3d¹⁰ 4s¹, not 3d⁴ 4s² and 3d⁹ 4s². The tool shows the actual configuration, with these exceptions, and the orbital diagram.
With the "Color" selector you can paint the table with a heat map of a property and see these trends at a glance. The melting point, by contrast, does not follow a simple rule: it depends on the type of bonding and the structure of the solid.
The molar mass of a compound is the sum of the atomic masses of its atoms, in g/mol. For water, H2O, with H = 1.008 and O = 15.999:
M = 2 · 1.008 + 15.999 = 18.015 g/mol
So 9.0 g of water is 9.0 / 18.015 ≈ 0.50 mol. The molar mass calculator does this for any formula, with parentheses and hydrates, step by step.
Standard atomic weights and their revisions are published by the IUPAC Commission on Isotopic Abundances and Atomic Weights (ciaaw.org). The theory in this guide is in general chemistry textbooks, for example R. Chang and K. A. Goldsby, Chemistry (McGraw-Hill), or T. L. Brown, H. E. LeMay, B. E. Bursten et al., Chemistry: The Central Science (Pearson). Simuveliq is not affiliated with IUPAC or with these authors or publishers.
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