d-block elements


The metallic elements are the most             

numerous of the elements and of
the metallic elements the d-block
elements are the most important:
their chemical properties are central
to both industry and contemporary
research. 
The two terms d-block metal and transition metal are often used interchangeably; however,
they do not mean the same thing. The name transition metal originally derived
from the fact that their chemical properties were transitional between those of the s and
p blocks. Now, however, the IUPAC definition of a transition element is that it is an
element that has an incomplete d subshell in either the neutral atom or its ions. Thus
the Group 12 elements (Zn, Cd, Hg) are members of the d block but are not transition
elements. In the following discussion, it will be convenient to refer to each row of the
d block as a series, with the 3d series the first row of the block (Period 4), the 4d series
the second row (Period 5), and so on. It will prove important to note the intrusion of the
f block, the inner transition elements, the lanthanoids, into the 5d series. Elements towards
the left of the d block are often referred to as early and those towards the right are referred
to as late.

Occurrence and recovery


The elements on the left of the 3d series occur in nature primarily as metal oxides or as metal
cations in combination with oxoanions . Of these elements, titanium ores are
the most difficult to reduce, and the element is widely produced by heating TiO2 with
chlorine and carbon to produce TiCl4, which is then reduced by molten magnesium at about
1000ºC in an inert-gas atmosphere. The oxides of Cr, Mn, and Fe are reduced with carbon
, a much cheaper reagent. To the right of Fe in the 3d series, Co, Ni, Cu, and
Zn occur mainly as sulfides and arsenides, which is consistent with the increasingly soft
Lewis acid character of their dipositive ions. Sulfide ores are usually roasted in air either to
the metal directly (for example, Ni) or to an oxide that is subsequently reduced (for example,
Zn). Copper is used in large quantities for electrical conductors; electrolysis is used to
refine crude copper to achieve the high purity needed for high electrical conductivity.
The difficulty of reducing the early 4d and 5d metals Mo and W is apparent from
. It reflects the tendency of these elements to have stable high oxidation states,
as discussed later. The platinum metals (Ru and Os, Rh and Ir, and Pd and Pt), which
are found at the lower right of the d block, occur as sulfide and arsenide ores, usually in
association with larger quantities of Cu, Ni, and Co. They are collected from the sludge
that forms during the electrolytic refinement of copper and nickel. Gold (and to some
extent silver) is found in its elemental form.

Location: Pakistan

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