In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinide elements (the f-block) are called inner transition metals and are sometimes considered to be transition metals as well.
Since they are metals, they are lustrous and have good electrical and thermal conductivity. Most (with the exception of group 11 and group 12) are hard and strong, and have high melting and boiling temperatures. They form compounds in any of two or more different oxidation states and bind to a variety of ligands to form coordination complexes that are often coloured. They form many useful alloys and are often employed as catalysts in elemental form or in compounds such as coordination complexes and oxides. Most are strongly paramagnetic because of their unpaired d electrons, as are many of their compounds. All of the elements that are ferromagnetic near room temperature are transition metals (iron, cobalt and nickel) or inner transition metals (gadolinium).
English chemist Charles Rugeley Bury (1890–1968) first used the word transition in this context in 1921, when he referred to a transition series of elements during the change of an inner layer of electrons (for example n = 3 in the 4th row of the periodic table) from a stable group of 8 to one of 18, or from 18 to 32.[1][2][3] These elements are now known as the d-block.
The first row of transition metals, in order
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^Bury, C. R. (1921). "Langmuir's theory of the arrangement of electrons in atoms and molecules". J. Am. Chem. Soc. 43 (7): 1602–1609. doi:10.1021/ja01440a023.
^Bury, Charles Rugeley. Encyclopedia.com Complete dictionary of scientific biography (2008).
Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. C. N. R. Rao, B. Raveau (1995). TransitionMetal Oxides. New York: VCH. ISBN 1-56081-647-3. Roesky, Herbert W.; Haiduc...
Metal carbonyls are coordination complexes of transitionmetals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts...
Transitionmetal hydrides are chemical compounds containing a transitionmetal bonded to hydrogen. Most transitionmetals form hydride complexes and some...
alkali metal chalcogenides often crystallize with the antifluorite structure and the alkaline earth salts in the sodium chloride motif. Transitionmetal chalcogenides...
of metallic bonds for different elemental metals reaches a maximum around the center of the transitionmetal series, as these elements have large numbers...
A transitionmetal carbene complex is an organometallic compound featuring a divalent carbon ligand, itself also called a carbene. Carbene complexes have...
Transitionmetal dinitrogen complexes are coordination compounds that contain transitionmetals as ion centers the dinitrogen molecules (N2) as ligands...
Metal nitrosyl complexes are complexes that contain nitric oxide, NO, bonded to a transitionmetal. Many kinds of nitrosyl complexes are known, which vary...
Transition-metal dichalcogenide (TMD or TMDC) monolayers are atomically thin semiconductors of the type MX2, with M a transition-metal atom (Mo, W, etc...
A transitionmetal alkoxide complex is a kind of coordination complex containing one or more alkoxide ligands, written as RO−, where R is the organic substituent...
hydrides. Classical transitionmetal hydride feature a single bond between the hydrogen centre and the transitionmetal. Some transitionmetal hydrides are acidic...
Transitionmetal complexes of thiocyanate describes coordination complexes containing one or more thiocyanate (SCN-) ligands. The topic also includes transition...
A transitionmetal oxo complex is a coordination complex containing an oxo ligand. Formally O2-, an oxo ligand can be bound to one or more metal centers...
as ligands or complexing agents. Many metal-containing compounds, especially those that include transitionmetals (elements like titanium that belong to...
In chemistry, a transitionmetal chloride complex is a coordination complex that consists of a transitionmetal coordinated to one or more chloride ligand...
In chemistry, a transitionmetal pincer complex is a type of coordination complex with a pincer ligand. Pincer ligands are chelating agents that binds...
considered metals, nonmetals, or semi-metals (sometimes called metalloids). Neither is there a consensus on what the metals succeeding the transitionmetals ought...
sometimes considered a lanthanide, despite being a d-block element and a transitionmetal. The informal chemical symbol Ln is used in general discussions of...
a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transitionmetals, and sometimes broadened to include metalloids...
In organometallic chemistry, a transitionmetal alkyne complex is a coordination compound containing one or more alkyne ligands. Such compounds are intermediates...
and seaborgium (Sg). These are all transitionmetals and chromium, molybdenum and tungsten are refractory metals. The electron configuration of these...
Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion (CH 3COCHCOCH− 3) and metal ions, usually transitionmetals. The...
context of the electronic spectroscopy of transitionmetal complexes. However, low-intensity f-f transitions in the actinide elements can be observed in...
technologically useful) electronic and magnetic properties, such as metal-insulator transitions, heavy fermion behavior, half-metallicity, and spin-charge separation...
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