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, with electron configurations ranging from s2d1 (Group 3) to s2d10 (Group 12). There are some irregularities in the sequence; for example Cr is s1d5 (not s2d4) and the Group 11 metals are s1d10 (not s2d9), 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 including only Groups 3-11 as transition metals. Group 12 metals lack the characteristic chemical and physical properties associated with incomplete d subshells and are considered post-transition metals. Jensen has reviewed the historical usage of the terms transition element (or metal) and d-block.
In the s-block and p-block of the periodic table, similar properties across the periods are generally not observed: the most important similarities tend to be vertical, down groups. However the d-block is notable in that horizontal similarities across the periods do become important.
Although Lutetium and Lawrencium are in the d-block, they are not considered transition metals but a lanthanide and an actinide, respectively, according to IUPAC. Group 12 elements are also in the d-block but are considered post-transition metals as their d-subshell is completely filled.
Chemical elements in d-block Group → 3 4 5 6 7 8 9 10 11 12 ↓ Period 4 21
- ^ a b R.H. Petrucci, W.S. Harwood and F.G. Herring “General Chemistry” (8th ed, Prentice-Hall 2002), p.341-2
- ^ a b C.E. Housecroft and A.G. Sharpe “Inorganic Chemistry” (2nd ed, Pearson Prentice-Hall 2005), p..20-21
- ^ F.A. Cotton and G. Wilkinson “Advanced Inorganic Chemistry” (5th ed, John Wiley 1988) p.625
- ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "transition element".
- ^ Jensen, William B. (2003). "The Place of Zinc, Cadmium, and Mercury in the Periodic Table". Journal of Chemical Education 80 (8): 952–961. Bibcode 2003JChEd..80..952J. doi:10.1021/ed080p952. http://www.uv.es/~borrasj/ingenieria_web/temas/tema_1/lecturas_comp/p952.pdf.
- ^ a b IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (online draft of an updated version of the "Red Book" IR 3-6)
Periodic tables Layouts List of elements by Groups Other element categories Blocks Periods
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