D-BLOCK ELEMENTS JEE Notes | EduRev

JEE : D-BLOCK ELEMENTS JEE Notes | EduRev

 Page 1


d-BLOCK ELEMENTS
1 . INTRODUCTION
(a) The element lying between s- and p-block element of the periodic table are collectively known as transition
or transitional elements. (T.E'.S.)
(b) Their properties are transitional between the highly electropositive s- block element to least electropositive
p-block element.
(c) In d- block elements, the last differentiating electron is accommodated to the penultimate shell.
(d) The general electronic configuration of transition element is (n-1)d
1-10
 ns
0, 1 or 2
(e) These elements either in their atomic state or in any of their common oxidation state have partly filled
(n-1)d orbitals of (n-1)
th
  main shell.
(f) The transition elements have an incompletely filled d-level. Since Zn, Cd, Hg elements have d
10
configuration and are not considered as transition elements but they are d-block elements.
ELECTRONIC CONFIGUR ATION
I
st 
Transation Series
Symbol Sc Ti V C r Mn Fe Co Ni C u Zn
Atomic No. 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0
3d electrons 1 2 3 5 5 6 7 8 1 0 1 0
4s electrons 2 2 2 1 2 2 2 2 1 2
Irregular electronic configuration Cr, Cu
II
nd
 Transation Series
Symbol Y Zr N b M o Tc R u R h P d A g Cd
Atomic No. 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8
4d electrons 1 2 4 5 5 7 8 1 0 1 0 1 0
5s electrons 2 2 1 1 2 1 1 0 1 2
Irregular electronic configuration Nb, Mo, Ru, Rh, Pd, Ag
III
rd
 Transation Series
Symbol L a Hf Ta W R e Os Ir P t A u Hg
Atomic No. 5 7 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0
5d electrons 1 2 3 4 5 6 7 9 1 0 1 0
6s electrons 2 2 2 2 2 2 2 1 1 2
Irregular electronic configuration W, Pt, Au
? ? The irregularities in the observed configuration of Cr (3d
5 
 4s
1 
 instead of 3d
4 
 4s
2  
), Cu (3d
10 
 4s
1 
), Mo (4d
5
5s
1
), Pd ([Kr] 4d
10
 5s
0 
), Au ( [Xe] 4f
14 
 5d
10 
 6s
1 
), Ag ([Kr] 4d
10 
 5s
1 
) are explained on the basis of the concept
that half-filled and completely filled d-orbitals are relatively more stable than other d-orbitals.
2 . GENERAL PROPERTIES OF d-BLOCK ELEMENTS
(a) The properties of d-block elements of any given period are not so much different from one another as
those of the same period of non transtion elements.
JEEMAIN.GURU
Page 2


d-BLOCK ELEMENTS
1 . INTRODUCTION
(a) The element lying between s- and p-block element of the periodic table are collectively known as transition
or transitional elements. (T.E'.S.)
(b) Their properties are transitional between the highly electropositive s- block element to least electropositive
p-block element.
(c) In d- block elements, the last differentiating electron is accommodated to the penultimate shell.
(d) The general electronic configuration of transition element is (n-1)d
1-10
 ns
0, 1 or 2
(e) These elements either in their atomic state or in any of their common oxidation state have partly filled
(n-1)d orbitals of (n-1)
th
  main shell.
(f) The transition elements have an incompletely filled d-level. Since Zn, Cd, Hg elements have d
10
configuration and are not considered as transition elements but they are d-block elements.
ELECTRONIC CONFIGUR ATION
I
st 
Transation Series
Symbol Sc Ti V C r Mn Fe Co Ni C u Zn
Atomic No. 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0
3d electrons 1 2 3 5 5 6 7 8 1 0 1 0
4s electrons 2 2 2 1 2 2 2 2 1 2
Irregular electronic configuration Cr, Cu
II
nd
 Transation Series
Symbol Y Zr N b M o Tc R u R h P d A g Cd
Atomic No. 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8
4d electrons 1 2 4 5 5 7 8 1 0 1 0 1 0
5s electrons 2 2 1 1 2 1 1 0 1 2
Irregular electronic configuration Nb, Mo, Ru, Rh, Pd, Ag
III
rd
 Transation Series
Symbol L a Hf Ta W R e Os Ir P t A u Hg
Atomic No. 5 7 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0
5d electrons 1 2 3 4 5 6 7 9 1 0 1 0
6s electrons 2 2 2 2 2 2 2 1 1 2
Irregular electronic configuration W, Pt, Au
? ? The irregularities in the observed configuration of Cr (3d
5 
 4s
1 
 instead of 3d
4 
 4s
2  
), Cu (3d
10 
 4s
1 
), Mo (4d
5
5s
1
), Pd ([Kr] 4d
10
 5s
0 
), Au ( [Xe] 4f
14 
 5d
10 
 6s
1 
), Ag ([Kr] 4d
10 
 5s
1 
) are explained on the basis of the concept
that half-filled and completely filled d-orbitals are relatively more stable than other d-orbitals.
2 . GENERAL PROPERTIES OF d-BLOCK ELEMENTS
(a) The properties of d-block elements of any given period are not so much different from one another as
those of the same period of non transtion elements.
JEEMAIN.GURU
(b) It is due to the fact that, in transition series, there is no change in number of electrons of outermost shell
and only change occur in (n-1)d electron from member to member in a period.
3 . METALLIC CHAR ACTER
(a) All the d-block elements are metals as the numbers of electrons in the outer most shell are one or two.
(b) They are hard, malleable and ductile (except Hg). IB group elements Cu, Ag and Au are most ductile and soft.
(c) These are good conducter of heat and electricity (due to free e
—
) Elements of IB group are most conductive
in nature. Their order of conductivity is  Ag > Cu > Au > Al
(d) Covalent and metallic bonding both exist in the atom of transition metals.
(e) The presence of partially filled d-subshell favour covalent bonding and metallic bonding. These bonding
are favourable also due to possession of one or two electron in outermost energy shell.
4 . REDUCING POWER
(a) Reducing power of d-block elements depends on their electrode potential.
(b) Standard oxidation potential (SOP) of Cu is minimum in the 3d series so it is least reducing elements in 3d
series.
(c) Au is the least reducing element in the d-block because of highest +ve value of Standard reduction potential.
(d) The poor reducing capacity of the transition metal is due to high heats of vaporization, high ionization
potential and low heat of hydration of their ions, because reduction potential depends upon all these
three factors.
5 . DENSITY
(a) The atomic volume of the transition elements are low, compared with s-block, so their density is
comparatively high (D = M/V)
(b) Os (22.57 gm cm
—3
) and Ir (22.61 gm cm
—3
) have highest density.
(c) In all the groups (except IIIB) there is normal increase in density from 3d to 4d series, and from 4d to 5d,
it increases just double. Due to lanthanide contraction Ex. Ti  <  Zr  <<  Hf
(d) In 3d series
                                                               Cu     Zn
Density increases
Density decreases
Sc    Ti    V    Cr     M n   Fe    Co    Ni
(e) In 3d series highest density – Cu lowest density – Sc
(f) Some important orders of density
Fe  <  Ni  <  Cu Fe  <  Cu  <  Au Fe  <  Hg  <  Au
6 . MELTING AND BOILING POINTS
(a) Melting and boiling point of d-block > s-block
Reason : Stronger metallic bond and presence of covalent bond formed by unpaired d-electrons.)
(b) In Zn, Cd, and Hg there is no unpaired electron present in d-orbital, hence due to absence of covalent
bond melting and boiling point are very low in series. (Volatile metals Zn, Cd, Hg)
(c) In 3d series  Sc to Cr  melting and boiling point  increases then Mn to Zn melting and boiling point decreases
(d) As the number of d-electron increases, the number of covalent bond between the atoms are expected to
increase up to Cr-Mo-W family where each of the d-orbital has only unpaired electrons and the opportunity
for covalent sharing is greatest.
(e) Mn and Tc have comparatively low melting point, due to weak metallic bond because of stable Half filled
(d
5
) configuration
JEEMAIN.GURU
Page 3


d-BLOCK ELEMENTS
1 . INTRODUCTION
(a) The element lying between s- and p-block element of the periodic table are collectively known as transition
or transitional elements. (T.E'.S.)
(b) Their properties are transitional between the highly electropositive s- block element to least electropositive
p-block element.
(c) In d- block elements, the last differentiating electron is accommodated to the penultimate shell.
(d) The general electronic configuration of transition element is (n-1)d
1-10
 ns
0, 1 or 2
(e) These elements either in their atomic state or in any of their common oxidation state have partly filled
(n-1)d orbitals of (n-1)
th
  main shell.
(f) The transition elements have an incompletely filled d-level. Since Zn, Cd, Hg elements have d
10
configuration and are not considered as transition elements but they are d-block elements.
ELECTRONIC CONFIGUR ATION
I
st 
Transation Series
Symbol Sc Ti V C r Mn Fe Co Ni C u Zn
Atomic No. 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0
3d electrons 1 2 3 5 5 6 7 8 1 0 1 0
4s electrons 2 2 2 1 2 2 2 2 1 2
Irregular electronic configuration Cr, Cu
II
nd
 Transation Series
Symbol Y Zr N b M o Tc R u R h P d A g Cd
Atomic No. 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8
4d electrons 1 2 4 5 5 7 8 1 0 1 0 1 0
5s electrons 2 2 1 1 2 1 1 0 1 2
Irregular electronic configuration Nb, Mo, Ru, Rh, Pd, Ag
III
rd
 Transation Series
Symbol L a Hf Ta W R e Os Ir P t A u Hg
Atomic No. 5 7 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0
5d electrons 1 2 3 4 5 6 7 9 1 0 1 0
6s electrons 2 2 2 2 2 2 2 1 1 2
Irregular electronic configuration W, Pt, Au
? ? The irregularities in the observed configuration of Cr (3d
5 
 4s
1 
 instead of 3d
4 
 4s
2  
), Cu (3d
10 
 4s
1 
), Mo (4d
5
5s
1
), Pd ([Kr] 4d
10
 5s
0 
), Au ( [Xe] 4f
14 
 5d
10 
 6s
1 
), Ag ([Kr] 4d
10 
 5s
1 
) are explained on the basis of the concept
that half-filled and completely filled d-orbitals are relatively more stable than other d-orbitals.
2 . GENERAL PROPERTIES OF d-BLOCK ELEMENTS
(a) The properties of d-block elements of any given period are not so much different from one another as
those of the same period of non transtion elements.
JEEMAIN.GURU
(b) It is due to the fact that, in transition series, there is no change in number of electrons of outermost shell
and only change occur in (n-1)d electron from member to member in a period.
3 . METALLIC CHAR ACTER
(a) All the d-block elements are metals as the numbers of electrons in the outer most shell are one or two.
(b) They are hard, malleable and ductile (except Hg). IB group elements Cu, Ag and Au are most ductile and soft.
(c) These are good conducter of heat and electricity (due to free e
—
) Elements of IB group are most conductive
in nature. Their order of conductivity is  Ag > Cu > Au > Al
(d) Covalent and metallic bonding both exist in the atom of transition metals.
(e) The presence of partially filled d-subshell favour covalent bonding and metallic bonding. These bonding
are favourable also due to possession of one or two electron in outermost energy shell.
4 . REDUCING POWER
(a) Reducing power of d-block elements depends on their electrode potential.
(b) Standard oxidation potential (SOP) of Cu is minimum in the 3d series so it is least reducing elements in 3d
series.
(c) Au is the least reducing element in the d-block because of highest +ve value of Standard reduction potential.
(d) The poor reducing capacity of the transition metal is due to high heats of vaporization, high ionization
potential and low heat of hydration of their ions, because reduction potential depends upon all these
three factors.
5 . DENSITY
(a) The atomic volume of the transition elements are low, compared with s-block, so their density is
comparatively high (D = M/V)
(b) Os (22.57 gm cm
—3
) and Ir (22.61 gm cm
—3
) have highest density.
(c) In all the groups (except IIIB) there is normal increase in density from 3d to 4d series, and from 4d to 5d,
it increases just double. Due to lanthanide contraction Ex. Ti  <  Zr  <<  Hf
(d) In 3d series
                                                               Cu     Zn
Density increases
Density decreases
Sc    Ti    V    Cr     M n   Fe    Co    Ni
(e) In 3d series highest density – Cu lowest density – Sc
(f) Some important orders of density
Fe  <  Ni  <  Cu Fe  <  Cu  <  Au Fe  <  Hg  <  Au
6 . MELTING AND BOILING POINTS
(a) Melting and boiling point of d-block > s-block
Reason : Stronger metallic bond and presence of covalent bond formed by unpaired d-electrons.)
(b) In Zn, Cd, and Hg there is no unpaired electron present in d-orbital, hence due to absence of covalent
bond melting and boiling point are very low in series. (Volatile metals Zn, Cd, Hg)
(c) In 3d series  Sc to Cr  melting and boiling point  increases then Mn to Zn melting and boiling point decreases
(d) As the number of d-electron increases, the number of covalent bond between the atoms are expected to
increase up to Cr-Mo-W family where each of the d-orbital has only unpaired electrons and the opportunity
for covalent sharing is greatest.
(e) Mn and Tc have comparatively low melting point, due to weak metallic bond because of stable Half filled
(d
5
) configuration
JEEMAIN.GURU
(f) Lowest melting point Hg  (– 38°C), Highest melting point W ( ~ 3400°C)
2000
1500
1000
500
0
III
B
IV
B
V
B
VI
B
VII
B
VIII I
B
II
B
Sc
1397
1672
Ti
V
1710
1900
Cr
Mn
1244
1530
Fe
Co
1495
Ni
1455
1083
Cu
420 Zn
Melting Point t/°C 
Graphic representation m.p. of 3d-series elem ents
Characteristic properties of transition elements :
(a) Variable oxidation state (b) Coloured ions (c) Paramagnetic properties
(d) Catalytic properties (e) Formation of alloys (f) Formation of interstitial compounds
(g) Formation of complexes.
7 . VARIABLE VALENCY OR VARIABLE OXIDATION STATES
(a) They exhibit variable valency due to involvement of (ns) and (n-1)d electrons. Due to less energy difference
between these electrons.
(b) The oxidation states of all transiition elements of '3d' series are as follows -
    Element         Conf. Outer electronic configuration Oxidation states
Sc 3d
1
4s
2  
+ 3
                3d                      4s
Ti 3d
2
4s
2
+ 2 + 3 + 4
V 3d
3
4s
2
+ 2 + 3 + 4 + 5
Cr 3d
5
4s
1
+ 1 + 2 + 3 + 4 +5  +6
Mn 3d
5
4s
2
+ 2 + 3 + 4 + 5 +6   +7
Fe 3d
6
4s
2
+ 2 + 3 + 4 + 6
Co 3d
7
4s
2
+ 2 + 3 + 4
Ni 3d
8
4s
2
+ 2 + 3 + 4
Cu 3d
10
4s
1
+ 1 + 2
Zn 3d
10
4s
2
+ 2
JEEMAIN.GURU
Page 4


d-BLOCK ELEMENTS
1 . INTRODUCTION
(a) The element lying between s- and p-block element of the periodic table are collectively known as transition
or transitional elements. (T.E'.S.)
(b) Their properties are transitional between the highly electropositive s- block element to least electropositive
p-block element.
(c) In d- block elements, the last differentiating electron is accommodated to the penultimate shell.
(d) The general electronic configuration of transition element is (n-1)d
1-10
 ns
0, 1 or 2
(e) These elements either in their atomic state or in any of their common oxidation state have partly filled
(n-1)d orbitals of (n-1)
th
  main shell.
(f) The transition elements have an incompletely filled d-level. Since Zn, Cd, Hg elements have d
10
configuration and are not considered as transition elements but they are d-block elements.
ELECTRONIC CONFIGUR ATION
I
st 
Transation Series
Symbol Sc Ti V C r Mn Fe Co Ni C u Zn
Atomic No. 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0
3d electrons 1 2 3 5 5 6 7 8 1 0 1 0
4s electrons 2 2 2 1 2 2 2 2 1 2
Irregular electronic configuration Cr, Cu
II
nd
 Transation Series
Symbol Y Zr N b M o Tc R u R h P d A g Cd
Atomic No. 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8
4d electrons 1 2 4 5 5 7 8 1 0 1 0 1 0
5s electrons 2 2 1 1 2 1 1 0 1 2
Irregular electronic configuration Nb, Mo, Ru, Rh, Pd, Ag
III
rd
 Transation Series
Symbol L a Hf Ta W R e Os Ir P t A u Hg
Atomic No. 5 7 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0
5d electrons 1 2 3 4 5 6 7 9 1 0 1 0
6s electrons 2 2 2 2 2 2 2 1 1 2
Irregular electronic configuration W, Pt, Au
? ? The irregularities in the observed configuration of Cr (3d
5 
 4s
1 
 instead of 3d
4 
 4s
2  
), Cu (3d
10 
 4s
1 
), Mo (4d
5
5s
1
), Pd ([Kr] 4d
10
 5s
0 
), Au ( [Xe] 4f
14 
 5d
10 
 6s
1 
), Ag ([Kr] 4d
10 
 5s
1 
) are explained on the basis of the concept
that half-filled and completely filled d-orbitals are relatively more stable than other d-orbitals.
2 . GENERAL PROPERTIES OF d-BLOCK ELEMENTS
(a) The properties of d-block elements of any given period are not so much different from one another as
those of the same period of non transtion elements.
JEEMAIN.GURU
(b) It is due to the fact that, in transition series, there is no change in number of electrons of outermost shell
and only change occur in (n-1)d electron from member to member in a period.
3 . METALLIC CHAR ACTER
(a) All the d-block elements are metals as the numbers of electrons in the outer most shell are one or two.
(b) They are hard, malleable and ductile (except Hg). IB group elements Cu, Ag and Au are most ductile and soft.
(c) These are good conducter of heat and electricity (due to free e
—
) Elements of IB group are most conductive
in nature. Their order of conductivity is  Ag > Cu > Au > Al
(d) Covalent and metallic bonding both exist in the atom of transition metals.
(e) The presence of partially filled d-subshell favour covalent bonding and metallic bonding. These bonding
are favourable also due to possession of one or two electron in outermost energy shell.
4 . REDUCING POWER
(a) Reducing power of d-block elements depends on their electrode potential.
(b) Standard oxidation potential (SOP) of Cu is minimum in the 3d series so it is least reducing elements in 3d
series.
(c) Au is the least reducing element in the d-block because of highest +ve value of Standard reduction potential.
(d) The poor reducing capacity of the transition metal is due to high heats of vaporization, high ionization
potential and low heat of hydration of their ions, because reduction potential depends upon all these
three factors.
5 . DENSITY
(a) The atomic volume of the transition elements are low, compared with s-block, so their density is
comparatively high (D = M/V)
(b) Os (22.57 gm cm
—3
) and Ir (22.61 gm cm
—3
) have highest density.
(c) In all the groups (except IIIB) there is normal increase in density from 3d to 4d series, and from 4d to 5d,
it increases just double. Due to lanthanide contraction Ex. Ti  <  Zr  <<  Hf
(d) In 3d series
                                                               Cu     Zn
Density increases
Density decreases
Sc    Ti    V    Cr     M n   Fe    Co    Ni
(e) In 3d series highest density – Cu lowest density – Sc
(f) Some important orders of density
Fe  <  Ni  <  Cu Fe  <  Cu  <  Au Fe  <  Hg  <  Au
6 . MELTING AND BOILING POINTS
(a) Melting and boiling point of d-block > s-block
Reason : Stronger metallic bond and presence of covalent bond formed by unpaired d-electrons.)
(b) In Zn, Cd, and Hg there is no unpaired electron present in d-orbital, hence due to absence of covalent
bond melting and boiling point are very low in series. (Volatile metals Zn, Cd, Hg)
(c) In 3d series  Sc to Cr  melting and boiling point  increases then Mn to Zn melting and boiling point decreases
(d) As the number of d-electron increases, the number of covalent bond between the atoms are expected to
increase up to Cr-Mo-W family where each of the d-orbital has only unpaired electrons and the opportunity
for covalent sharing is greatest.
(e) Mn and Tc have comparatively low melting point, due to weak metallic bond because of stable Half filled
(d
5
) configuration
JEEMAIN.GURU
(f) Lowest melting point Hg  (– 38°C), Highest melting point W ( ~ 3400°C)
2000
1500
1000
500
0
III
B
IV
B
V
B
VI
B
VII
B
VIII I
B
II
B
Sc
1397
1672
Ti
V
1710
1900
Cr
Mn
1244
1530
Fe
Co
1495
Ni
1455
1083
Cu
420 Zn
Melting Point t/°C 
Graphic representation m.p. of 3d-series elem ents
Characteristic properties of transition elements :
(a) Variable oxidation state (b) Coloured ions (c) Paramagnetic properties
(d) Catalytic properties (e) Formation of alloys (f) Formation of interstitial compounds
(g) Formation of complexes.
7 . VARIABLE VALENCY OR VARIABLE OXIDATION STATES
(a) They exhibit variable valency due to involvement of (ns) and (n-1)d electrons. Due to less energy difference
between these electrons.
(b) The oxidation states of all transiition elements of '3d' series are as follows -
    Element         Conf. Outer electronic configuration Oxidation states
Sc 3d
1
4s
2  
+ 3
                3d                      4s
Ti 3d
2
4s
2
+ 2 + 3 + 4
V 3d
3
4s
2
+ 2 + 3 + 4 + 5
Cr 3d
5
4s
1
+ 1 + 2 + 3 + 4 +5  +6
Mn 3d
5
4s
2
+ 2 + 3 + 4 + 5 +6   +7
Fe 3d
6
4s
2
+ 2 + 3 + 4 + 6
Co 3d
7
4s
2
+ 2 + 3 + 4
Ni 3d
8
4s
2
+ 2 + 3 + 4
Cu 3d
10
4s
1
+ 1 + 2
Zn 3d
10
4s
2
+ 2
JEEMAIN.GURU
(c) Highest oxidation state of transition elements can be calculated by n + 2 where (n = number of
unpaired electrons)  It is not applied for Cr and Cu.
(d) The transition metal ions having stable configuration like d
0 
 d
5
 or d
10 
 are more stable.
Ex. Sc
+3
,  Ti
+4
,  V
+5
,
  Fe
+3 
,  Mn
+2
,  Zn
+2 
 etc.
(e) In aqueous medium Cr
+3
 is stable.
(f) Co
+3
 and Ni
+2
 are stable in complexes..
(g) In aqeous medium due to disproportionation Cu
+1 
is less stable than Cu
+2 
 while its configuration is 3d
10
(h) Most common oxidation state among the transition elements is +2.
(i) Highest oxidation state shown by transition elements of '4d' and '5d' series is +8 by Ru (44) and Os (76).
(j) The common oxidation state shown by elements of IIIB i.e., Sc, Y, La and Ac is +3 as their divalent
compounds are highly unstable.
(k) In lower oxidation state transition elements form ionic compounds and in higher oxidation state their
compounds are covalent.
(l) They also shows zero oxidation state in their carbonyl compounds like Ni(CO)
4
.
(m) Usually transition metal ions in their lower oxidation state act as reducing agents and in higher oxidation
state they are oxidising agents.
Ex. Sc
+2
,  Ti
+2
,  V
+2
,  Fe
+2
,  Co
+2
  etc are reducing agents
Cr
+6
,  Mn
+7
,  Mn
+6
,  Mn
+5
,  Mn
+4
  etc are oxidising agents.
The relative stability of various oxidation states
(a) The relative stabilities of various oxidation states of 3d-series element can be correlated with the extra
stability of 3d°,3d
5 
 & 3 d
10 
 configuration to some extent.
Ex. Stability of  Ti
4+ 
(3d
0
)  >  Ti
3 + 
(3d
1 
)Mn
2+ 
(3d
5
)  >  Mn
3+ 
(3d
4
)
(b) The higher oxidation state of 4d and 5d series element are generally more stable than the elements of 3d
series. Ex.
(i)
vi -2
4
Mo O (oxidation state of Mo is +6), 
vi -2
4
Mo O (4d series) & 
vi 2
4
W O
?
 
, 
vii
4
Re O
?
 (5d series) are more
stable due to their maximum oxidation state.
(ii)
vi 2
4
Cr O
?
 & 
vii
4
Mn O
?
(3d-series) are strong oxidizing agents.
(c) Strongly reducing states probably do not form fluorides or oxides, but may well form the heavier halides
Conversely, strong oxidizing state form oxides & fluoride, but not Bromide and lodide. Ex.
(i) V (Vanadium) react with halogens to form VF
5 
 VCl
5 
, VBr
3
,but doesn' t form VBr
5 
or VI
5 
because in + 5
oxidation state Vanadium is strong oxidizing agent thus convert Br 
– 
 & I
– 
 to Br
2 
 & I
2 
respectively, So VBr
3
&VI
3 
are formed but not VBr
5 
 & VI
5.
(ii) On the other hand VF
5 
 is formed because V
5+ 
ion unable to oxidize highly electronegative & small anion F
–
(iii) Similarly highly electronegative and small O
2 – 
ion formed oxides Ex. VO
4 
3 –
,
 
CrO
4
2– 
 & MnO
4
– 
etc.
JEEMAIN.GURU
Page 5


d-BLOCK ELEMENTS
1 . INTRODUCTION
(a) The element lying between s- and p-block element of the periodic table are collectively known as transition
or transitional elements. (T.E'.S.)
(b) Their properties are transitional between the highly electropositive s- block element to least electropositive
p-block element.
(c) In d- block elements, the last differentiating electron is accommodated to the penultimate shell.
(d) The general electronic configuration of transition element is (n-1)d
1-10
 ns
0, 1 or 2
(e) These elements either in their atomic state or in any of their common oxidation state have partly filled
(n-1)d orbitals of (n-1)
th
  main shell.
(f) The transition elements have an incompletely filled d-level. Since Zn, Cd, Hg elements have d
10
configuration and are not considered as transition elements but they are d-block elements.
ELECTRONIC CONFIGUR ATION
I
st 
Transation Series
Symbol Sc Ti V C r Mn Fe Co Ni C u Zn
Atomic No. 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0
3d electrons 1 2 3 5 5 6 7 8 1 0 1 0
4s electrons 2 2 2 1 2 2 2 2 1 2
Irregular electronic configuration Cr, Cu
II
nd
 Transation Series
Symbol Y Zr N b M o Tc R u R h P d A g Cd
Atomic No. 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8
4d electrons 1 2 4 5 5 7 8 1 0 1 0 1 0
5s electrons 2 2 1 1 2 1 1 0 1 2
Irregular electronic configuration Nb, Mo, Ru, Rh, Pd, Ag
III
rd
 Transation Series
Symbol L a Hf Ta W R e Os Ir P t A u Hg
Atomic No. 5 7 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0
5d electrons 1 2 3 4 5 6 7 9 1 0 1 0
6s electrons 2 2 2 2 2 2 2 1 1 2
Irregular electronic configuration W, Pt, Au
? ? The irregularities in the observed configuration of Cr (3d
5 
 4s
1 
 instead of 3d
4 
 4s
2  
), Cu (3d
10 
 4s
1 
), Mo (4d
5
5s
1
), Pd ([Kr] 4d
10
 5s
0 
), Au ( [Xe] 4f
14 
 5d
10 
 6s
1 
), Ag ([Kr] 4d
10 
 5s
1 
) are explained on the basis of the concept
that half-filled and completely filled d-orbitals are relatively more stable than other d-orbitals.
2 . GENERAL PROPERTIES OF d-BLOCK ELEMENTS
(a) The properties of d-block elements of any given period are not so much different from one another as
those of the same period of non transtion elements.
JEEMAIN.GURU
(b) It is due to the fact that, in transition series, there is no change in number of electrons of outermost shell
and only change occur in (n-1)d electron from member to member in a period.
3 . METALLIC CHAR ACTER
(a) All the d-block elements are metals as the numbers of electrons in the outer most shell are one or two.
(b) They are hard, malleable and ductile (except Hg). IB group elements Cu, Ag and Au are most ductile and soft.
(c) These are good conducter of heat and electricity (due to free e
—
) Elements of IB group are most conductive
in nature. Their order of conductivity is  Ag > Cu > Au > Al
(d) Covalent and metallic bonding both exist in the atom of transition metals.
(e) The presence of partially filled d-subshell favour covalent bonding and metallic bonding. These bonding
are favourable also due to possession of one or two electron in outermost energy shell.
4 . REDUCING POWER
(a) Reducing power of d-block elements depends on their electrode potential.
(b) Standard oxidation potential (SOP) of Cu is minimum in the 3d series so it is least reducing elements in 3d
series.
(c) Au is the least reducing element in the d-block because of highest +ve value of Standard reduction potential.
(d) The poor reducing capacity of the transition metal is due to high heats of vaporization, high ionization
potential and low heat of hydration of their ions, because reduction potential depends upon all these
three factors.
5 . DENSITY
(a) The atomic volume of the transition elements are low, compared with s-block, so their density is
comparatively high (D = M/V)
(b) Os (22.57 gm cm
—3
) and Ir (22.61 gm cm
—3
) have highest density.
(c) In all the groups (except IIIB) there is normal increase in density from 3d to 4d series, and from 4d to 5d,
it increases just double. Due to lanthanide contraction Ex. Ti  <  Zr  <<  Hf
(d) In 3d series
                                                               Cu     Zn
Density increases
Density decreases
Sc    Ti    V    Cr     M n   Fe    Co    Ni
(e) In 3d series highest density – Cu lowest density – Sc
(f) Some important orders of density
Fe  <  Ni  <  Cu Fe  <  Cu  <  Au Fe  <  Hg  <  Au
6 . MELTING AND BOILING POINTS
(a) Melting and boiling point of d-block > s-block
Reason : Stronger metallic bond and presence of covalent bond formed by unpaired d-electrons.)
(b) In Zn, Cd, and Hg there is no unpaired electron present in d-orbital, hence due to absence of covalent
bond melting and boiling point are very low in series. (Volatile metals Zn, Cd, Hg)
(c) In 3d series  Sc to Cr  melting and boiling point  increases then Mn to Zn melting and boiling point decreases
(d) As the number of d-electron increases, the number of covalent bond between the atoms are expected to
increase up to Cr-Mo-W family where each of the d-orbital has only unpaired electrons and the opportunity
for covalent sharing is greatest.
(e) Mn and Tc have comparatively low melting point, due to weak metallic bond because of stable Half filled
(d
5
) configuration
JEEMAIN.GURU
(f) Lowest melting point Hg  (– 38°C), Highest melting point W ( ~ 3400°C)
2000
1500
1000
500
0
III
B
IV
B
V
B
VI
B
VII
B
VIII I
B
II
B
Sc
1397
1672
Ti
V
1710
1900
Cr
Mn
1244
1530
Fe
Co
1495
Ni
1455
1083
Cu
420 Zn
Melting Point t/°C 
Graphic representation m.p. of 3d-series elem ents
Characteristic properties of transition elements :
(a) Variable oxidation state (b) Coloured ions (c) Paramagnetic properties
(d) Catalytic properties (e) Formation of alloys (f) Formation of interstitial compounds
(g) Formation of complexes.
7 . VARIABLE VALENCY OR VARIABLE OXIDATION STATES
(a) They exhibit variable valency due to involvement of (ns) and (n-1)d electrons. Due to less energy difference
between these electrons.
(b) The oxidation states of all transiition elements of '3d' series are as follows -
    Element         Conf. Outer electronic configuration Oxidation states
Sc 3d
1
4s
2  
+ 3
                3d                      4s
Ti 3d
2
4s
2
+ 2 + 3 + 4
V 3d
3
4s
2
+ 2 + 3 + 4 + 5
Cr 3d
5
4s
1
+ 1 + 2 + 3 + 4 +5  +6
Mn 3d
5
4s
2
+ 2 + 3 + 4 + 5 +6   +7
Fe 3d
6
4s
2
+ 2 + 3 + 4 + 6
Co 3d
7
4s
2
+ 2 + 3 + 4
Ni 3d
8
4s
2
+ 2 + 3 + 4
Cu 3d
10
4s
1
+ 1 + 2
Zn 3d
10
4s
2
+ 2
JEEMAIN.GURU
(c) Highest oxidation state of transition elements can be calculated by n + 2 where (n = number of
unpaired electrons)  It is not applied for Cr and Cu.
(d) The transition metal ions having stable configuration like d
0 
 d
5
 or d
10 
 are more stable.
Ex. Sc
+3
,  Ti
+4
,  V
+5
,
  Fe
+3 
,  Mn
+2
,  Zn
+2 
 etc.
(e) In aqueous medium Cr
+3
 is stable.
(f) Co
+3
 and Ni
+2
 are stable in complexes..
(g) In aqeous medium due to disproportionation Cu
+1 
is less stable than Cu
+2 
 while its configuration is 3d
10
(h) Most common oxidation state among the transition elements is +2.
(i) Highest oxidation state shown by transition elements of '4d' and '5d' series is +8 by Ru (44) and Os (76).
(j) The common oxidation state shown by elements of IIIB i.e., Sc, Y, La and Ac is +3 as their divalent
compounds are highly unstable.
(k) In lower oxidation state transition elements form ionic compounds and in higher oxidation state their
compounds are covalent.
(l) They also shows zero oxidation state in their carbonyl compounds like Ni(CO)
4
.
(m) Usually transition metal ions in their lower oxidation state act as reducing agents and in higher oxidation
state they are oxidising agents.
Ex. Sc
+2
,  Ti
+2
,  V
+2
,  Fe
+2
,  Co
+2
  etc are reducing agents
Cr
+6
,  Mn
+7
,  Mn
+6
,  Mn
+5
,  Mn
+4
  etc are oxidising agents.
The relative stability of various oxidation states
(a) The relative stabilities of various oxidation states of 3d-series element can be correlated with the extra
stability of 3d°,3d
5 
 & 3 d
10 
 configuration to some extent.
Ex. Stability of  Ti
4+ 
(3d
0
)  >  Ti
3 + 
(3d
1 
)Mn
2+ 
(3d
5
)  >  Mn
3+ 
(3d
4
)
(b) The higher oxidation state of 4d and 5d series element are generally more stable than the elements of 3d
series. Ex.
(i)
vi -2
4
Mo O (oxidation state of Mo is +6), 
vi -2
4
Mo O (4d series) & 
vi 2
4
W O
?
 
, 
vii
4
Re O
?
 (5d series) are more
stable due to their maximum oxidation state.
(ii)
vi 2
4
Cr O
?
 & 
vii
4
Mn O
?
(3d-series) are strong oxidizing agents.
(c) Strongly reducing states probably do not form fluorides or oxides, but may well form the heavier halides
Conversely, strong oxidizing state form oxides & fluoride, but not Bromide and lodide. Ex.
(i) V (Vanadium) react with halogens to form VF
5 
 VCl
5 
, VBr
3
,but doesn' t form VBr
5 
or VI
5 
because in + 5
oxidation state Vanadium is strong oxidizing agent thus convert Br 
– 
 & I
– 
 to Br
2 
 & I
2 
respectively, So VBr
3
&VI
3 
are formed but not VBr
5 
 & VI
5.
(ii) On the other hand VF
5 
 is formed because V
5+ 
ion unable to oxidize highly electronegative & small anion F
–
(iii) Similarly highly electronegative and small O
2 – 
ion formed oxides Ex. VO
4 
3 –
,
 
CrO
4
2– 
 & MnO
4
– 
etc.
JEEMAIN.GURU
Diffrent oxidation state of chloride &  oxides compound
+2
TiCl
2
TiCl
3
VCl
2
VCl
3
(Ionic, basic) Less ionic 
(Am photeric)
TiCl
4
VCl
4
VOCl
3
Covalent and Acidic 
(Strong lewis acid)
+3 +4 +5 +6 +7
TiO
VO
CrO
M nO
Ti O
2 3
VO
2 3
Cr O
2 3
M nO
2 3
TiO
2
M nO
2 
VO
2 5
CrO
3
M nO
3 
M nO
2 7 
Less Ionic (Am photeric) Ionic, basic Acidic, covalent
(d) Such compounds are expected to be unstable except in case where vacant d-orbitals are used for accepting
lone-pair from ?-bonding ligand.
Ex. [Ni(CO)
4
], [Ag(CN)
2
]
–
 ,[Ag)(NH
3
)
2
]
+
8 . COLOUR PROPERTY
(a) Most of the transition metal ions exhibit colour property.
(b) This is due to d-d transition of unpaired electrons in their t
2g 
and e
g
 sets of 'd' orbitals.
(c) They require less amount of energy to undergo excitation of electrons. Hence they absorb visible region
of light exhibiting colour.
Ex. Sc
+2 
 : [Ar]3d
1
,  Ti
+2  
: [Ar]3d
2
,  V
+2 
: [Ar]3d
3
(d) Transition metal ions which do not have any unpaired elctrons in their 'd' orbitals like 3d
0
 and 3d
10
configurations, do not exhibit any colour property.
Ex. Sc
+3
 : [Ar]3d
0
, Cu
+1 
:
 
[Ar]3d
10
, Ti
+4 
:
 
[Ar]3d
0
 etc are colourless ions.
(e) A transition metal ion absorbs a part of visible region of light and emmits rest of the colours, the combination
of which, is the colour of emitted light. The colour of metal ion is the colour of the emitted light.
(f) In transition metal ion the 'd' orbitals split into lower energy set t
2g
 orbitals and higher energy set e
g
 orbitals.
The electrons from t
2g
 set get excited to higher energy set i.e., e
g
 set. This excitation of electrons is called
as 'd-d' transition. Due to this 'd -d' transition the transition metal ions exhibit colour property.
              
d
x
2
y
2d
z
2
-
d
yz
d
xy
d
yz
d-orbitals (degenerate)
light
Lower energy set = t
2g
H igher energy set = e
g
Presence of ligands d-d T rnsition
(t )
2g
(e)
g
Factors affecting the colour of complex
The colour of a transition metal complex depends on-
(a) The magnitude of energy difference between the two d-levels ( ? ?
0 
)
,
JEEMAIN.GURU
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