The transition metals (d-block elements)


There are three complete series (from period 4-6 in the group 3-12) and one incomplete series (period 7th) of the transition elements.

 

3d series (4th period) : Scandium (21SC) to Zinc (30Zn)

4d series (5th period) : Yttrium (39Y) to Cadmium (48Cd)

5d series (6th period) : Lanthanum (57La) to Mercury

(80Hg) except 58Ce to 71Lu

6d series (7th period) : Begins with Actinium (89AC) and is still complete. It does not include actinoids i.e., the elements from 90Th to 103Lr.

The general outer most electronic configuration of d-block elements is (n − 1)d1 − 10 ns1−2, where n = outermost shell. Following chart describes the outer shell electronic configurations of transition elements in ground state:

Table: Outer Electronic Configurations of the Transition Elements (ground state)

1st Series

 

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

Z

21

22

23

24

25

26

27

28

29

30

4s

2

2

2

1

2

2

2

2

1

2

3d

1

2

3

5

5

6

7

8

10

10



2nd Series

 

Y

Zr

Nb

Mo

Tc

Ru

Rh

Pd

Ag

Cd

Z

39

40

41

42

43

44

45

46

47

48

5s

2

2

1

1

1

1

1

0

1

2

4d

1

2

4

5

6

7

8

10

10

10



3rd Series

 

La

Hf

Ta

W

Re

Os

Ir

Pt

Au

Hg

Z

57

72

73

74

75

76

77

78

79

80

6s

2

2

2

2

2

2

2

1

1

2

5d

1

2

3

4

5

6

7

9

10

10



4th Series

 

Ac

Rf

Db

Sg

Bh

Hs

Mt

Ds

Rg

Uub

Z

89

104

105

106

107

108

109

110

111

112

7s

2

2

2

2

2

2

2

2

1

2

6d

1

2

3

4

5

6

7

8

10

10

 

The electronic configurations of Zn, Cd and Hg are represented by general formula (n − 1)d10 ns2 and these elements have completely filled d-orbitals in ground state as well as in their common oxidation states. Hence, they are not considered as transition elements. On the other hand, silver (47Ag) has also completely filled d-orbitals in ground state, but in +2 oxidation state it has 4d9 configuration which is incomplete, thus silver is considered to be transition element.