d & f block class 12 chapter notes

1. Element/symbol Atomic number Electronic configuration
Scandium (Sc) 21 [Ar13d'452
Arl3d 4s2
Ar13d4s2
Titanium (Ti) 22
Vanadium (V) 23
Arl3d54s
Ar13d4
Chromium* (Cr) 24
Manganese (Mn) 25
Arl3d 42
Ar13d4s2
Iron (Fe) 26
Cobalt (Co) 27
Nickel (Ni) 28 Arl3d4s2
Copper (Cu) 29 [Ar13d14s
Zinc (Zn) 30 Arl3d 452
Exceptional configuration of Cr and Cu
It may be noted that the configurations of chromium, [Ar]3d°4s' and copper, [Ar]3d"4s are anomalous. This unexcepted electronic
configuration can be explained on the basis of half-filled and completely flled subshell which are found to be most stablearrangements
The
extra stability of half-filled subshells results from the occupation of each orbital by one electron resulting in spreading and
equal distribution of charge around the atom. In case of copper, it appears that Cu, [Ar]3d4s' with filled 3dsubshell andhalf
filed 4s-subshell is more stable than [Ar|3 d'4s. Another important factor which explain the stability of these configurations i
their large exchange energy.
The electrons in various orbitals of the same subshell or in different subshell can exchange their respective positions, during this
exchange process, a small amount of energy is released. The released energy is called exchange energy. It has been tound that
exchange energy is maximum when all the orbitals of same subshell are either completely filled or exactly half-filled.This is because
maximum exchanges take place under these conditions, giving the configuration of Cr, [Ar]3d°45' and Cu, [Arl3d"4s' extra stability.
C (7 1 ) Tho

2. General Trends in the Properties of Transition Elements
The d-block elements have similar nsorbital electronic configuration in the outermost energy shell, n, and theydifforfsa
only in the number of electrons in the d-orbitals of the penultimate shell, (n- 1). Since only thepenultimatechalneanother
these elements is expanding, they may have resemblance in their physical and chemical properties. The d&-block plaCons of
metals. They have high melting and boiling points and have higher heat
of vapourisation
than non-transitionelemen dre hard
The transition metals and their compounds also exhibit catalytic property and magnetc benaviour. Ihere are areater cimil de
in the properties of the transition elements of a horizontal row in contrast to the non-transition elements. However com
similarities also exist.
mone another
enultimate shell of
electrons of
me
group
Atomic radii
The atomic radii of transition elements are intermediate between those of s- and p-block elements. The following trend in atomi.
radii of elements of d-block are observed tomic
Along the period: As we move from left to right in a period, the atomic radii of elements of a particular series dectreace s
increase in atomic number but this decrease in atomic radii becomes smaller after midway and becomes almostconstantandthon
increases towards theendofthe period. For example,the atomic radius of first transitionseries decreases fromSetoCr and then
remains almost constant til Cu and then increases towards the end. The atomic radii of dblock elements are given inthetable
Atomic radii of d- block elements (in pm)
with
3dseries Sc T Cr Mn Fe Co Ni Cu Zn
128 137
164 147 135 129 137 126 125 125
4dseries Y Zr Nb Mo TC Ru Rh Pd Ag
144
Cd
180 160 146 139 136 134 134 137 151
5dseriesLa Hf Ta W Re Os Ir Pt Au Hg
187 159 146 139 137 135 136 139 144 151
Explanation In the beginning, the atomic radius decreases in a period
because with increase in atomic number, the nuclear charge goes on increasing
(by unity) progressively. However the increased nuclear charge is partly
cancelled by the increased screening effect of electrons in the d-orbitals of
the penultimate shel. When the increased nuclear charge and increased
screening effect balance each other, the atomic radii become almost constant.
Increase in atomic radii towards the end may be attributed to the electron
electron repulsions. In fact, the pairing of electrons in the d-orbitals occur
after d configuration. The repulsive interactions between the paired electrons
in d-orbitals become very dominant towards the end of the period and cause
the expansion of electron cloud and thus, resulting in increase of atomic size.
Similar behaviour has been observed for the second and third transition series.
6
12
-Sc Ti VCr Mn Fe Co N Cu n
Zr Nb Mo Tc Ru Rh Pd Ag Cd
La Hf Ta W Re Os Ir Pt Au Hg
Along the group:The atomic radii increase as we move down the group.
Therefore, the atomic radii of transition element of second series have larger
Trends in atomic radil of transition
elements

3. valuesthan those offirsttransition series. However, the transition elements of third series have nearly the same radii as metals of
secondtransition series above them.
Explanation: The atomic radii of elements of second transition series are more than those of first transition series because the
electrons in the atoms of second transition series elements occupy energy levels farther from the nucleus. With an increase in
number ofeutermost shell, size also increases. The similar atomic radii of elements of second and third transition series are due to
lanthanoid tontraction. This is associated with 4forbitals which are filled before the elements of Sd-seriesstarts
onieradi
The trend followed by the ionic radi is the same as that followed by atomic radii. lonic radii of transition metals are different in
diferent oxidation states.In general, the ionic radii decrease with increase in oxidation state. Thus, the ionic size of M* cations
aresmallerthan that of M* cations. This is because the ionic radius decreases with increase in effective nuclear charge. However,
theionictaciof cations in the same oxidation state decrease with increase in atomic number as shown in table below
Variation of ionic radii of first transition series (in pm)
Element SC V Cr Mn Fe Co Ni Cu Zn
M2
M3
82 77 4 70 75
79 82 73
73 67 64 62 65 65 61 60
Metalliccharacier and enthalpy of atomisation
All the transition elements have typical metallic structure except mercury which is a liquid. They have simple hcp, ccp or bcc lattices.
Theypossess high enthalpies of atomisation.
Explanation: The metallic character oftransition elements is due to
theirrelativelylow ionisation enthalpies and number of vacant orbitals
inthe outermost shell. The hardness of these metals suggest that
the presence of strong bonding due to overlap of unpaired electrons
betweendifferent metal atoms, therefore, these elements exhibit high
enthalpiesof atomisation (i.e., heat required to break the metal lattice
togetfreeatoms)as shown in figure. The maxima at about the middle
ofeachseries indicates that one unpaired electron per d-orbital is
favourable for strong inter-atomic interactions. In general, greater
thenumber of unpaired delectrons, greater is the strength of these
bonds.Thus,as we move from left to right in a dseries, the number of
unpairedelectrons increases from 1 to 6 and then decreases to zero in
Caseof group 12. C, Mo and Whave maximum number of unpaired
electronsandtherefore these are very hard metals and have maximum
enthalpiesof atomisation. The elements Zn, Cd and Hg do not have
anyunpaired electrons, therefore, these are not very hard metals.
900-
-Series 3
-Series 2
Series 1
800
700
600
500
400
300
200
100
0-
Atomic number
Trends in enthalpies of atomization A,H (kJ mol)
of transition elements
Densily
Alltransition metals have high density. Density is the ratio of mass to volume. As we move in a period, the densities increase because
atomicradi decrease due to increase in effective nuclear charge. Therefore, the atomic volume decreases, but at the same time atomic
massincreases. Hence, density also increases.
Variation of density (g cm ) in first transition series
Ti V Cr Mn Fe Co Ni
89 11
Element Sc Cu Zn
6.07 7.19 7.217.8
Density 3.43 4.1 8.7 8.9 8.9 7.1
Down thegroup, the density increases because very less variation in atomic volume is observedwhereas atomic mass increases.
Thedensites of second transition series are higher than those of first transition series and the densities of third transition series
arestilhigher.
Explanation: The atomic volumes of the transition elements are low because the electrons are added in (n - 1) &subshell and
notinnssubshell.Therefore, the increased nuclear charge is poorly screened by the delectrons and the outer electrons are strongly
attactedbythe nucleus. Moreover, the added electrons occupy inner orbitals. Consequently, the densities of transition metals are high.

4. Different oxidation states of elements of first, second and third transition series
First Transition Series
Sc Ti Cr Mn Fe Co Ni Cu Zn
(+2) (+2) +2 +2 +2 +2 +2 +2 +1 +2
+3 +3 +3 +3 +3 +3 +3 +3 +2
+4 (+4)
(+5)
+4 +4 +4) (+4) +4
+5 (+5)
+6 +6 (+6)
+7
Second Transition Series
Y Zr Nb
(+3) (+2)
Mo Tc Rh
+2
Ru Pd
+2
Ag Cd
+3 +2 +2 +2 +1 +2
+4 (+3) +3 (+4) +3 +3 (+3) (+2)
(+4) +4 (+5) +4 +4 +4 (+3)
+5 +5 (+5) (+6)
(+6)
+6 (+7)
(+8)

5. Magnetic properties
Most of the transition elements and their compounds show paramagnetism. A substance which is attracted by magnetic field is
called paramagnetic substance and the phenomenon is called paramagnetism. The paramagnetism first increases in any
etic
transi
field is
series and then decreases.
The maximum paramagnetism is seen in the middle of the series. The magnetic moments of first transition series are ias t.
table below. en in the
lon Outer electronic Number of Magnetic Moment
Calculated
configuration unpaired electrons
Observed
Sc3+ 3d
3d
3d2
0 0 0
T+ 1 1.73 1.75
T2
y2+
2 2.84 2.76
3d3 3 3.87 3.86
C2 3d4 4 4.90 4.80
Mn+ 3d 5 5.92 5.96
Fe 3d6 4 4.90 5.3-5.5
Co2
Ni2
3d 3 3.87 4.4-5.2
3a8 2 2.84 2.9-3.4
Cu2+ 349 1 1.73 1.8-2.2
Zn 3d10 0 0
Explanation Paramagnetism arises due to presence of unpaired electrons in atoms,ions or molecules and it is describedinterms
of Bohr magneton (B.M.).
The magnetic moment of first transition series can be calculated by the following relation (assuming no contribution from the orbital
magnetic moment) =Jn(n+2)B.M.
where, n is the number of unpaired electrons and u is magnetic moment in Bohr magneton (B.M.) unit. It is clear from the above table that
as the number of unpaired electrons increases from 1to 5, the magnetic moment increases and hence, paramagneticcharacteralso increases

6. Electronic configurations of lanthanoids
Element
Lanthanum
Cerium
Praseodymium
Neodymium
Promethium
Samarium
Europium
Gadolinium
Terbium
Atomic number Electronicconfiguration
Symbol
La 57
Xe] 5d'6
Xe] 4f 5d' 63
Xel 4f 5d063
Xel 4f 5d 63
Xe] 4f 5d 63
Xel 4 5d 6
Xe] 4f 5d 6
Xel 4f 5d'63
Xe] 4 5d 6
Xel 4fl0sd°6
Xe] 4f sdo652
Xe]4/25d 6
Xe] 4r3 5d 6
Xel 4f sd 63
Xe] 4f45d'63
Ce 58
Pr 59
Nd 60
Pm 61
Sm 62
Eu 63
Gd 64
Tb 65
Dysprosium
Holmium
Erbium
Thulium
Dy 66
Ho 67
Er 68
Tm 69
Ytterbium
Lutetium
Yb 70
Lu 71
tis clear from the above table that Lanthanum, La (Z=57) hasthe electronic configuration [Xe]5d'6s. However, in the succeeding 14
elements, 14 electrons are successively added to the 4-Subshel. For example, the next electron after lanthanum, enters the 4f-subshell
and confiquration of cerium is [Xe]4f"5d'65.The filling of 4-orbital continues till wereach ytterbium in which 4fsubshell gets completely
filled as:Yb (7= 70): [Xe] 4f" 65. The single 50-electron shifts to the 44-subshell in all cases except in gadolinium, Gd where such a
shift gives the symmetry of half flled 4fsubshell and in lutetium, Lu where the 4fsubshell has already been completelyfiled
Atomic or lonic radii: The atomic and ionic radii of tripositive ions (M*") show a steady and gradual decrease in moving from La to
Lu as shown in the figure below. Although the atomic radii show irregularities but ionic radii decreases steadily from La to Lu.
Lanthanoid contraction : The steady decrease in the size of lanthanoid ions with the increase in atomic number is called lanthanoid
contraction.
Cause of lanthanoid contraction : As the atomic number increases in
lanthanoid series, for eveny proton in the nucleus the extra electron goes to fill
4forbitals. The 4f-electrons contribute inner shells and are rather ineffective in
screening the nuclear charge. Thus, there is a gradual increase in the effective
nuclear charge experienced by the outer electrons. Consequently, the attraction
of the nucleus for the electrons in the outermost shell increases as the atomic
number of lanthanoid increases and the electron cloud shrinks. This results in
gradual decrease in size of lanthanoids with increase in atomic number.
Consequence of lanthanoid contraction: The important consequences of
lanthanoid contraction are:
() Resemblance of second and third transition series: Because ofthis
contraction in size across the lanthanoid series, elements which follow the third
transition series are considerably smaller than would otherwise beexpected.The
normal size increases from Sc YLa and the size of any atom of the third
transition series (after La) is nearly same as that of the atom of the element lying
in the same group of the second transition series. Thus, pair of elements such as
Zr-H, Nb-Ta and Mo-W are almost identical in size. Due to almost similar size,
such pairs have similar properties
(i) Separation of lanthanoids Allthe lanthanoids have quite similar
properties and due to this reason they are difficult toseparate. However, because
of Lanthanoid contraction their properties varyslightly.This slight variationin
properties is utilized in the separation of lanthanoids by ion exchange methods.
(ii) Variation in basic strength of hydroxides: The basic strength of hydroxides decreases from La(OH) to Lu
lanthanoid contraction, size of M" ions decreases and there is an increase in the covalent character in the M-OH bond.
Sm+
110
Eu2
Ce
P r 3 s
N o 3
Pm
3*
100
m
E y3+
*
9 C e d
bPr4
Ho
+
90
m *
o T 6 *
5759 6165 676911
Atomic number
Trends In ionic radii of lanthanoids
Due
to

7. lanthanoids, actinidesalsoform complexes. However, actinideshave greatertendency to form complexes
mplexes: Like l
tjon Oanthanides. This is because of their high charge and smaller size of their ions.
nCmpanisonto
nTheactinoid ions in generalare coloured. The separation of colour depends upon the number of 5f-electrons. The ions containing
iauless while those having 2to 6 electrons in 5f-subshell are coloured.
C o l o u r
a n d 57 are
Colours of actinoid ions in aqueous solutions
lon Numberof electrons Colour
Colourless
Red
Blue orpurple
Violet
Pink
Colourless
Colourless
Colourless
Ac3+
U3+
Np
Pu3+
Am3+
Cm3+
Th4 0
Pa+
U4+ 2
Green
Yellow-green
Np4+
Pu44 4
Orange
Pink
Pale-yellow
Am4+
Cm4+
lonio radii and actinoid contraction: Like lanthanoids, actinoids also show contraction called actinoid contraction. The size of atoml
ration dedrease regularly along the actino0Id series. The steady decrease in ionic radii with increase in atomic number is called actinoid
contaction. This is due to poor shielding of 5felectrons. The magnitude of actinoid contraction is more that of lanthanoid contraction.
Oxidation states: The common oxidation state ofthese elements is +3. However, they also exhibit oxidation state of +2, +4, +5, +6
gnd+7. Thus, actinoids exhibit greater range of oxidation states. This wide range is attributed to the fact that the 5f, 6d and 7s energy
vels are of comparable energies. Therefore, all these three subshells can participate. The common known oxidation states of actinoids
zerecorded in the table below:
Oxidation state of actinium and actinoids
Element Electronic configuration Oxidation states
Outerelectron configuration of
M3 M+
Ac Rn]6d 73
IRn]5 6d 73
IRn)5f 6d73
Rn]5f 6d 7
[Rn]5f 6d 73
Rn)566 73
IRn)5f 67
[Rn]5f'6d 73
Rn]5f 6d 7
IRn)5f 6 73
IRn]5f 6d 73
IRn]5f 6 73
IRn]5 6 73
IRn) 5f4 6d 7
IRn)546d' 7
+3 5f0
Th +3, +4 5f' 5f
Pa +3,+4, +5
+3, +4,+5,+6
+3,+4,+5,+6,+7
+3,+4,+5,+6,+7
+3,+4,+5,+6
+3,
5f
5/P 5f
Np 53
Pu 5f 5f4
Am 5f
5
Cm
* * * * * ********
5f 5f0
Bk +3, +4 5f8 5f
+3 5f9 5f8
ES 5f10 5f
5f10
5f1
5f12
5f13
m 3
Md
No
5fl2
5f13
5f14
+3
Hcinoids Lr 3
d toher e compounas in +3 state than in the +4 state. In this respect they resemble lanthanoids. The lower oxidation states
Wnile the higher ones are covalent. +2, +3 and +4 ions are hydrolysed quite readily.

8. Chemical reactivity : The actinoids are reactive metals Iike lanthanoids. They tarnish in air duo to
with hot water. The actinoids react with most non-metdist uede temperatures. Ihese metals reactrod XIde coating. Thau
nitric acid is slower due to formation of protective
oxide Tiim. Ihe metals are basic and do not reart ddlily with HCI ht y react
OH. th
Comparison of actinoid and lanthanoid series
Both lanthanoids and actinoids involve the filling of -orbitals. iney snow close resemblance in c o .
many properties.
Similarities
between
lanthanoids andactinoids
Both exhio forbitals are
Deeactinoidcontrac as well as lanthanides are soluble while hydroxides, fluorides and
orhitals. They show close esemoldnce in some of their properties but also differ in
1. Both exhibit oxidation state of +3 predominantly.
2. In both the series, forbitals are being progressively
filled.
3. Just like lanthanoid
contraction we have actinoid
contraction.
rivalent actinides as well as lantnanides are soluble while hydroxides,fluorides and
4. The nitrates, perchlorates and sulphates of trivalent actinides as well as lanthanides are
In the absorption spectra of elements of both the series sharp line-like bunch appear due to fftramute
5.
carbonates are insoluble.
tion.
Difference between lanthanoids and actinoids: Ihe important points ofdifferences between lanthanei
summed up below:
Lanthanoids
Actinoids
Property In addition to +3 oxidation state, actinoids also show
higheroxidation states such as +4, +5, +6 and +7.For
example, uranium exhibits oxidation states of +3, +4, +5
and +6. +6 Oxidation state is stable in compounds such
as UF6, U0;.
Binding energies of 5fare lower.
1. Oxidation states Lanthanoids show mainly +3 oxidation state
except in a few cases where it is +2 and +4
2. Binding energies Binding energies of 4fare higher.
3. Shielding effect 4felectrons have greater shielding eftect. Iherefore, 5T electrons nave poor shielding effect. Therefore.the
Contraction in their sizes is more.
the contraction in their ionic radii is less.
The tendency to torm complexes is more.
The tendency to form complexes is less.
4. Tendency to
form complexes
5. Basic character Lanthanoid compounds are less basic. Actinoids compounds are more basic.
6. Tendency to They do not form oxO-1ons. They form oxo-ions such as UOz, NpOz, Pu0, U0*.
form oxo ions
7. Radioactivity Except promethium, these are non-radioactive. All the actinoids are radioactive.
Most ofthe actinoid ions are coloured. For example,U3*
(red), U (green), UOS" (yellow)
8. Colours Most of their ions are colourless.
9. Paramagnetic
character
They are paramagnetic and their magnetic They are als0 paramagnetic but their magnetic properties
properties can be easily explained.
cannot be easily explained as they are more complex.
Uses of actinoids
1. Thorium is used in atomic reactors as fuel rods and in treatment of cancer. A mixture of thorium and cerium nitrate in theratoo
99% is used for making incandescent gas mantles
Uranium is used as nuclear fuel in nuclear reactors.
1.
3. Uranium salts are used in glass industry and also in medicines.
2.
4. Plutonium is used as fuel for atomic reactors as well as in atomic bombs.
4.