Transition Metal

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Transition Metal
Transition Metal
In chemistry, the term transition metal (sometimes also called a transition element) has two
possible meanings:
The IUPAC definition states that a transition metal is "an element whose atom has an
incomplete d sub-shel , or which can give rise to cations with an incomplete d sub-shel ".
Most scientists describe a "transition metal" as any element in the d-block of the periodic
table, which includes groups 3 to 12 on the periodic table. All elements in the d-block are
metals. In actual practice, the f-block is also included in the form of the lanthanide and actinide
Transition Metals Definition
The elements belonging to 3 to 12 group, present in the center of the periodic table are called
as transition metals.
These are actually d- block metals and form a bridge in between the s and p block elements,
the metals and non metals.
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The transition metals are unique among the chemical elements. The elements in which last
electron enters the d- sub shel of their penultimate shel (n-1 shell) are known as d- block
Thus, transition metals can be broadly defined as those which either as elements or as ions
have partial y fil ed d-subshell. Since d-subshell is partially filled, the elements are cal ed as d-
block elements.
The transition metals are classified into four transition series. Each series (Except 6d) consists
of 10 elements. (This is because the d- sub-shell can occupy only 10 electrons and they get
filled up when we move along a period in a series.)
Characteristics of Transition Metals
The transition metals properties are described as fol ows.
Transition elements have partly fil ed d- orbitals. These elements show several interesting
properties like variable oxidation state or variable valency, formation of colored complexes
and paramagnetic behaviors. These metals and their compounds also exhibit catalytic
Some of the important properties of transition metals are
1. Electronic Configuration
The electronic configurations of transition elements may in general be represented as
(n-1) d 1-10 ns1 or 2
The (n-1) means penultimate or next to the outermost shel and d- orbital may have 1 to 10
electrons and the s- orbital of the outermost shel (n) may have 1 or 2 electrons. The
electronic configurations of all the four series of elements are given in a table above.
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2. Atomic and ionic radii
The atomic and ionic radi of the elements of a particular transition series decreases from left
to right.
In the first series, the atomic radii become almost constant for chromium, because of two
factors-Increase in nuclear charge and increase in the screening effect which just balance
each other.
Atomic radi of Chromium is - 117pm. Mn, the next element has an atomic radi of 117 pm. The
next three elements, Co, Ni and Cu has 116. 115 and 117 respectively.
To summarize, atomic and ionic radii decrease with increase in atomic number, due to
increase in nuclear charge.
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