JEEMAIN.GURU
d-BLOCK ELEMENTS
1. I NT RO DU CT IO N
(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)d1-10 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 Tra nsat ion Serie s
Symbol Sc Ti V Cr Mn Fe Co Ni Cu Zn
Atomic No. 21 22 23 24 25 26 27 28 29 30
3d electrons 1 2 3 5 5 6 7 8 10 10
4s electrons 2 2 2 1 2 2 2 2 1 2
Ir regular electronic configurat ion Cr, Cu
II nd Tra nsat ion Serie s
Symbol Y Zr Nb Mo Tc Ru Rh Pd Ag Cd
Atomic No. 39 40 41 42 43 44 45 46 47 48
4d electrons 1 2 4 5 5 7 8 10 10 10
5s electrons 2 2 1 1 2 1 1 0 1 2
Irregular electronic configuration Nb, Mo, Ru, Rh, Pd, Ag
III r d Tra nsat ion Serie s
Symbol La Hf Ta W Re Os Ir Pt Au Hg
Atomic No. 57 72 73 74 75 76 77 78 79 80
5d electrons 1 2 3 4 5 6 7 9 10 10
6s electrons 2 2 2 2 2 2 2 1 1 2
Ir regular electronic configurat ion W, Pt, Au
The irregularities in the observed configuration of Cr (3d5 4s1 instead of 3d4 4s2 ), Cu (3d10 4s1 ), Mo (4d5
5s1), Pd ([Kr] 4d10 5s0 ), Au ( [Xe] 4f14 5d10 6s1 ), Ag ([Kr] 4d10 5s1 ) 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
Sc Ti V Cr Mn Fe Co Ni Cu Zn
Density increases Density decreases
(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
(d5 ) configuration
,JEEMAIN.GURU
(f) Lowest melting point Hg (– 38°C), Highest melting point W ( ~ 3400°C)
2000
1900
1672 V Cr 1530 Co 1455
Melting Point t/°C
1500 Sc Ti 1710 Mn Fe
1495 Ni
1397 1083
1244
Cu
1000
420 Zn
500
0 B
B
III IV
B
V
B
VI
B
VII
B
VIII I B
II
Graphic representation m.p. of 3d-series elements
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. VARIA BLE VALENCY OR VARIA BLE 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
d-BLOCK ELEMENTS
1. I NT RO DU CT IO N
(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)d1-10 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 Tra nsat ion Serie s
Symbol Sc Ti V Cr Mn Fe Co Ni Cu Zn
Atomic No. 21 22 23 24 25 26 27 28 29 30
3d electrons 1 2 3 5 5 6 7 8 10 10
4s electrons 2 2 2 1 2 2 2 2 1 2
Ir regular electronic configurat ion Cr, Cu
II nd Tra nsat ion Serie s
Symbol Y Zr Nb Mo Tc Ru Rh Pd Ag Cd
Atomic No. 39 40 41 42 43 44 45 46 47 48
4d electrons 1 2 4 5 5 7 8 10 10 10
5s electrons 2 2 1 1 2 1 1 0 1 2
Irregular electronic configuration Nb, Mo, Ru, Rh, Pd, Ag
III r d Tra nsat ion Serie s
Symbol La Hf Ta W Re Os Ir Pt Au Hg
Atomic No. 57 72 73 74 75 76 77 78 79 80
5d electrons 1 2 3 4 5 6 7 9 10 10
6s electrons 2 2 2 2 2 2 2 1 1 2
Ir regular electronic configurat ion W, Pt, Au
The irregularities in the observed configuration of Cr (3d5 4s1 instead of 3d4 4s2 ), Cu (3d10 4s1 ), Mo (4d5
5s1), Pd ([Kr] 4d10 5s0 ), Au ( [Xe] 4f14 5d10 6s1 ), Ag ([Kr] 4d10 5s1 ) 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
Sc Ti V Cr Mn Fe Co Ni Cu Zn
Density increases Density decreases
(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
(d5 ) configuration
,JEEMAIN.GURU
(f) Lowest melting point Hg (– 38°C), Highest melting point W ( ~ 3400°C)
2000
1900
1672 V Cr 1530 Co 1455
Melting Point t/°C
1500 Sc Ti 1710 Mn Fe
1495 Ni
1397 1083
1244
Cu
1000
420 Zn
500
0 B
B
III IV
B
V
B
VI
B
VII
B
VIII I B
II
Graphic representation m.p. of 3d-series elements
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. VARIA BLE VALENCY OR VARIA BLE 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
