# List of misidentified chemical elements

Chemical elements that have been mistakenly "discovered". Further investigation showed that their discovery was either mistaken, that they have been mistaken from an already-known element, or mixture of two elements, or that they indicated a failing in theory where a new element had been assumed rather than some previously unknown behaviour.
| Name | Symbol | Atomic number | Actual element | Discovery date | Discoverer | |
| Alabamium | Ab | 85 | Astatine | 1931 | Fred Allison | |
| Alkalinium | | 87 | Francium | 1926 | Gerald J. F. Druce, Frederick H. Loring | |
| Anglohelvetium | | | | | | See Helvetium |
| Arconium | | | | 1911 | J. W. Nicholson | |
| Asterium | | | | 1898 | Norman Lockyer, Carl David Tolmé Runge, Friedrich Paschen | |
| Aurorium | | | | 1874 | William Huggins | |
| Ausenium | Ao | 93 | Neptunium | 1934 | Enrico Fermi | |
| Austrium | | 31 | Gallium | 1886 | Eduard Linnemann | Hypothesised from spectral line observations in the rare-earth mineral orthite. It was later confirmed that these lines were due to the recently discovered gallium. |
| Berzelium | Bz | 90 | Thorium | 1901 | Charles Baskerville | See Carolinium |
| Bohemium | | 93 | Neptunium | 1934 | Odolen Koblic | |
| Carolinium | Cn | 90 | Thorium | 1901 | Charles Baskerville | With Berzelium, erroneously identified as a mixture of three elements, with thorium, during work at the University of North Carolina. |
| Coronium | | 26 | Iron | 1869 | Charles Augustus Young and William Harkness | Hypothesised from a 530.3 nm green emission line in the solar coronal spectrum. Later, around 1902, renamed as Newtonium. In the 1930s recognised as highly ionized iron, rather than a new element. |
| Cyclonium | | 61 | Promethium | 1941 | H. B. Law, Ohio State University | |
| Dakin | Dk | 85 | Astatine | 1937 | Rajendralal De Cepare | |
| Davyum | | | Iridium and rhodium | 1877 | Serge Kern | |
| Decipium | | | Samarium and other rare earths | 1878 | Marc Delafontaine | Thought to have been isolated from the mineral samarskite in 1878. |
| Dianium | | | Niobium and tantalum | 1860 | Wolfgang Franz von Kobell | See Pelopium |
| Didymium | | | Praseodymium and neodymium | 1841 | Carl Mosander | |
| Dorine | | 85 | Astatine | 1936 | Horia Hulubei, Yvette Cauchois | |
| Eka-caesium | | 87 | Francium | | | |
| Eka-rhenium | | 107 | Bohrium | | | |
| Florentium | | 61 | Promethium | 1924 | Luigi Rolla and Lorenzo Fernandes | |
| Ghiorsium | Gh | 118 | Oganesson | 1999 | Lawrence Berkeley National Laboratory | |
| Gnomium | | | Similarities to nickel and iron | 1892 | Gerhard Krüss and F. W. Schmidt | Not discovered, but hypothesised to explain discrepancies within the iron group elements for an early periodic table ordered by mass. The concept of atomic number clarified the situation without requiring the invention of a new element. |
| Helvetium | | 85 | Astatine | 1940 | Walter Minder | Rediscovered [sic] in 1942 and named Anglohelvetium |
| Hesperium | Hs | 94 | Plutonium | 1934 | Enrico Fermi | |
| Illinium | | 61 | Promethium | 1926 | Smith Hopkins and Len Yntema, University of Illinois at Urbana–Champaign | |
| Ilmenium | | | Niobium and tantalum | 1847 | R. Hermann | See Pelopium |
| Lucium | | 39 | Yttrium | 1896 | Prosper Barrière | |
| Masurium | | 43 | Technetium | 1925 | Walter Noddack, Otto Berg, Ida Noddack | |
| Moldavium | Mi | 87 | Francium | 1936 | Horia Hulubei, Yvette Cauchois | |
| Monium | | | | 1898 | | See Victorium |
| Muriaticum | | 17 | Chlorine | 1774 | Carl Wilhelm Scheele | |
| Murium | | | | 1785 | Claude Louis Berthollet | |
| Nebulium | | | Oxygen | 1864 | William Huggins | |
| Neutronium | | 0 | (Neutronium) | 1926 | Andreas von Antropoff | |
| Newtonium | | | | 1902 | | See Coronium |
| Ninovium | Nv | 118 | Oganesson | 1999 | Victor Ninov | Studies proved inconsistencies in the data shown from Victor Ninov |
| Nipponium | Np | 75 | Rhenium | 1908 | Masataka Ogawa | |
| Pelopium | | | Niobium and tantalum | 1846 | Heinrich Rose | Confused with mixtures of the difficult to distinguish niobium and tantalum, extracted from the mineral tantalite. |
| Polinium | | 77 | Iridium | 1828 | Gottfried Osann | |
| Ptene | | 76 | Osmium | 1803 | Hippolyte-Victor Collet-Descotils, Antoine François, comte de Fourcroy, Louis Nicolas Vauquelin, Smithson Tennant | |
| Protyle | | | | 1816 | William Prout | |
| Russium | | 87 | Francium | 1925 | D. K. Dobroserdov | |
| Sergenium | Sg | 108 | Hassium | 1963 | Victor Cherdyntsev | |
| Sequanium | | 93 | Neptunium | 1939 | Horia Hulubei | Thought to have been present in tantalite ore, actually not present, rather than mis-identified. |
| Unbibium | Ubb | 122 | (Unbibium) | 2008 | Amnon Marinov | |
| Victorium | | | Gadolinium and terbium | 1898 | William Crookes | |
| Virginium | Vi (Vm) | 87 | Francium | 1930 | Fred Allison | |
| Wasium | | | Mixture of rare earths | 1862 | J. F. Bahr | Another element identified in ores from Ytterby. |