The d-block is the portion of the periodic table that contains the element groups 3-12. These groups correspond to the filling of the atomic d-orbital subshell of the second outermost shell (inside an outermost shell only containing 1 or 2 s-orbital electrons) with electron configurations ranging from sd (Group 3) to sd (Group 12). There are some irregularities in the sequence; for example Cr is sd (not sd) and the Group 11 metals are sd (not sd)...
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The d-block is the portion of the periodic table that contains the element groups 3-12. These groups correspond to the filling of the atomic d-orbital subshell of the second outermost shell (inside an outermost shell only containing 1 or 2 s-orbital electrons) with electron configurations ranging from sd (Group 3) to sd (Group 12). There are some irregularities in the sequence; for example Cr is sd (not sd) and the Group 11 metals are sd (not sd), so that the d-subshell is actually complete at Group 11.
The d-block elements are often also known as transition metals or transition elements. However the exact limits of the transition metal region are usually not considered to be identical to the d-block. Although some authors do identify the entire d-block as transition metals, most define transition metals as elements with partly filled d subshells either in the neutral atom or in ions in common oxidation states. This definition has now been adopted by IUPAC, and corresponds to...
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