THE TRANSITION METALS
INTRODUCTION
The elements from scandium (atomic number 21) to zinc (atomic number 30) in the periodic table
form what is generally regarded as the first sequence of transition elements. But what exactly is
a transition element and why is it that these elements have similarities to each other across their
period, a feature which is not apparent in other parts of the periodic table?
The answer to these and other questions concerning the transition metals lies in their electronic
structures. Indeed, virtually all the properties of transition elements are related to their
electronic structures and the relative energy levels of the orbitals available for their electrons.
The electron structures of atoms and ions of the elements K to Zn.
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, ELEMENT SYMBOL ELECTRONIC COMMON ELECTRONIC
STRUCTURE ION STRUCTURE OF
OF ATOM ION
POTASSIUM K (Ar) 4S1 K+ (Ar)
CALCIUM Ca (Ar) 4S2 Ca2+ (Ar)
SCANDIUM Sc (Ar) 3d1 4S2 Sc3+ (Ar)
TITANIUM Ti (Ar) 3d2 4S2 Ti4+ (Ar)
VANADIUM V (Ar) 3d3 4S2 V3+ (Ar) 3d2
CHROMIUM Cr (Ar) 3d5 4S1 Cr3+ (Ar) 3d3
MANGANESE Cr (Ar) 3d5 4S2 Mn2+ (Ar) 3d5
IRON Fe (Ar) 3d6 4S2 Fe2+ (Ar) 3d6
Fe2+ (Ar) 3d5
COBALT Co (Ar) 3d74S2 Co2+ (Ar) 3d7
NICKEL Ni (Ar) 3d8 4S2 Ni2+ (Ar) 3d8
COPPER Cu (Ar) 3d10 4S1 Cu+ (Ar) 3d10
Cu2+ (Ar) 3d9
ZINC Zn (Ar) 3d10 4S2 Zn2+ (Ar) 3d10
As the shells of electrons get further and further from the nucleus, successive shells become
closer in energy. Thus, the difference in energy between the second and third shells is less than
that between the first and second. By the time the fourth shell is reached, there is, in fact, an
overlap between the third and fourth shells. In other words, from Scandium onwards, the
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INTRODUCTION
The elements from scandium (atomic number 21) to zinc (atomic number 30) in the periodic table
form what is generally regarded as the first sequence of transition elements. But what exactly is
a transition element and why is it that these elements have similarities to each other across their
period, a feature which is not apparent in other parts of the periodic table?
The answer to these and other questions concerning the transition metals lies in their electronic
structures. Indeed, virtually all the properties of transition elements are related to their
electronic structures and the relative energy levels of the orbitals available for their electrons.
The electron structures of atoms and ions of the elements K to Zn.
1
, ELEMENT SYMBOL ELECTRONIC COMMON ELECTRONIC
STRUCTURE ION STRUCTURE OF
OF ATOM ION
POTASSIUM K (Ar) 4S1 K+ (Ar)
CALCIUM Ca (Ar) 4S2 Ca2+ (Ar)
SCANDIUM Sc (Ar) 3d1 4S2 Sc3+ (Ar)
TITANIUM Ti (Ar) 3d2 4S2 Ti4+ (Ar)
VANADIUM V (Ar) 3d3 4S2 V3+ (Ar) 3d2
CHROMIUM Cr (Ar) 3d5 4S1 Cr3+ (Ar) 3d3
MANGANESE Cr (Ar) 3d5 4S2 Mn2+ (Ar) 3d5
IRON Fe (Ar) 3d6 4S2 Fe2+ (Ar) 3d6
Fe2+ (Ar) 3d5
COBALT Co (Ar) 3d74S2 Co2+ (Ar) 3d7
NICKEL Ni (Ar) 3d8 4S2 Ni2+ (Ar) 3d8
COPPER Cu (Ar) 3d10 4S1 Cu+ (Ar) 3d10
Cu2+ (Ar) 3d9
ZINC Zn (Ar) 3d10 4S2 Zn2+ (Ar) 3d10
As the shells of electrons get further and further from the nucleus, successive shells become
closer in energy. Thus, the difference in energy between the second and third shells is less than
that between the first and second. By the time the fourth shell is reached, there is, in fact, an
overlap between the third and fourth shells. In other words, from Scandium onwards, the
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