transition elements


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transition elements

or

transition metals,

in chemistry, group of elements characterized by the filling of an inner d electron orbital as atomic number increases. This includes the elements from titanium to copper, and those lying in the columns below them in the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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. Many of the chemical and physical properties of the transition elements are due to their unfilled d orbitals. In the elements of the lanthanide serieslanthanide series,
a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series.
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 and the actinide seriesactinide series,
a series of radioactive metallic elements in Group 3 of the periodic table. Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series.
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 the inner f orbital is filled as atomic number increases; those elements are often called the inner transition elements. Transition elements generally exhibit high density, high melting point, magnetic properties, variable valence, and the formation of stable coordination complexes. Their variable valence is due to the electrons in the d orbitals. The study of the complex ionscomplex ion,
charged molecular aggregate (see ion), consisting of a metallic atom or ion to which is attached one or more electron-donating molecules. In some complex ions, such as sulfate, SO4−2
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 and compounds formed by transition metals is an important branch of chemistry. Many of these complexes are highly colored and exhibit paramagnetism.

Transition Elements

 

(also called transition metals), the 61 chemical elements that fall into subgroups IB through VIIIB in D. I. Mendeleev’s periodic system of the elements. With respect to atomic structure, transition elements are characterized by unfilled inner electron shells. Transition elements are divided into d-elements and f-elements: in the d-elements electrons are added to the 2d-, 4d-, 5d-, and 6d-subshells, and in the f-elements electrons are added to the 4f-subshell in the lanthanides and the 5f-subshell in the actinides. These electron configurations account for certain specific properties of transition elements, including the ability to form complexes and to exhibit ferromagnetism. (See.)

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We therefore turn attention to the transition elements, or transition metals, which Wald mentions in passing.
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