Chemical Elements
Chemical elements and their symbols, weights, discovery years, and credited discoverers.
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| ID | Element | Symbol | Weight | Discovered | Discovered by | Discovery notes | Weight type |
|---|---|---|---|---|---|---|---|
| 1 | Actinium | Ac | 227.0000 | 1899 | Andre-Louis Debierne | Isotope mass number | |
| 2 | Aluminum | Al | 26.9820 | 1825 | Hans Oersted | Standard atomic weight | |
| 3 | Americium | Am | 243.0000 | 1944 | Glenn Seaborg and colleagues | Isotope mass number | |
| 4 | Antimony | Sb | 121.7600 | Unknown | Known in antiquity; no single discovery year or discoverer is recorded. | Standard atomic weight | |
| 5 | Argon | Ar | 39.9500 | 1894 | Lord Rayleigh and Sir William Ramsay | Standard atomic weight | |
| 6 | Arsenic | As | 74.9220 | 1250 | Albertus Magnus | Approximate date in the RSC reference. | Standard atomic weight |
| 7 | Astatine | At | 210.0000 | 1940 | Dale R. Corson, Kenneth Ross MacKenzie, Emilio Segrè | Isotope mass number | |
| 8 | Barium | Ba | 137.3300 | 1808 | Humphry Davy | Standard atomic weight | |
| 9 | Berkelium | Bk | 247.0000 | 1949 | Stanley Thompson, Albert Ghiorso, and Glenn Seaborg | Isotope mass number | |
| 10 | Beryllium | Be | 9.0122 | 1798 | Louis Nicolas Vauquelin | Discovery announced in 1798; metal isolated independently by Friedrich Wohler and Antoine Bussy in 1828. | Standard atomic weight |
Scope and sources
Last checked against sources: October 14, 2026.
Last changed: October 13, 2026. This is when we last changed the data or its description. It doesn’t mean the data runs up to that date.
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