The document summarizes key information about d-block and f-block elements. It discusses: - The d-block elements have their d orbitals progressively filled in each period, while the f-block elements have their 4f and 5f orbitals filled in the latter two periods. - Transition metals exhibit a variety of oxidation states, melting points, atomic radii, and magnetic properties due to their incompletely filled d orbitals. - Properties vary periodically across each series as the nuclear charge increases, with factors like ionization energies and electronegativity influencing stability and reactivity.

1. d – AND f – BLOCK ELEMENTS
TINTO JOHNS M. Sc., M. Ed

3. • The d-block of the periodic table contains the
elements of the groups 3-12 in which the d
orbitals are progressively filled in each of the four
long periods.
• The elements constituting the f -block are those
in which the 4 f and 5 f orbitals are progressively
filled in the latter two long periods.
• There are mainly three series of the transition
metals, 3d series (Sc to Zn), 4d series (Y to Cd)
and 5d series (La to Hg, omitting Ce to Lu). The
fourth 6d series which begins with Ac is still
incomplete. The two series of the inner
transition metals, (4f and 5f) are known as
lanthanoids and actinoids respectively.

5. • A transition element is defined as
the one which has incompletely
filled d orbitals in its ground state
or in any one of its oxidation states.
• Zinc, cadmium and mercury of group 12 have
full d10 configuration in their ground state as
well as in their common oxidation states and
hence, are not regarded as transition metals

6. Position in the Position in the Periodic Table Periodic
Table
• The d–block occupies the large middle section
flanked by s– and p– blocks in the periodic table.
• Electronic Configurations of the d-Block of the d-
Block Elements
• General the electronic configuration (n-1)d1–10ns1–2.
• Half and completely filled sets of orbitals are
relatively more stable. A consequence of this factor
is reflected in the electronic configurations of Cr and
Cu in the 3d series. Consider the case of Cr, for
example, which has 3d5 4s1 instead of 3d4 4s2.

7. Physical properties
• The transition metals (with the exception of
Zn, Cd and Hg) are very much hard and have
low volatility. Their melting and boiling points
are high.

8. MELTING POINT AND BOILING POINT
• High M.P and B.P - Due to strong metallic bond
and the presence of half filled d- orbitals
• Involvement of greater number of electrons
from (n-1)d in addition to the ns electrons in
the inter atomic metallic bonding.
• Because of stronger interatomic bonding
High enthalpy of atomisation transition
elements have high M.P and B.P

9. • In moving along the period from left to right,
the M.P of these metals first INCREASES to
MAXIMUM and the DECREASES regularly
towards the end of the period.

10. • melting points of these metals rise to a maximum at
d5 except for anomalous values of Mn and Tc and fall
regularly as the atomic number increases.
TRENDS OF M.P OF 3- d , 4-d AND 5-d TRANSITION
METALS
• The strength of interatomic bonds in transition
elements is roughly related to the number of half
filled d- orbitals
• In the beginning the no. of half filled d- orbitals
increases till the middle of the period causing
increase in strength of interparticle bonds But
thereafter the pairing of electrons in d – orbitals
occurs and the no. of half filled orbitals decreases ,
which also cause decrease in M.P

11. Trends in enthalpies of atomization of transition elements
1. Greater the number of valence electrons, stronger the
inter atomic attraction, hence stronger bonding
between atoms resulting in higher enthalpies of
atomization.
2. metals of the second and third series have greater
enthalpies of atomization than the corresponding
elements of the first series

12. Atomic and ionic radii
• The Atomic/ionic radii first DECREASES till the
middle, becomes almost constant and then
INCREASES towards the end of the period.
• New electron enters a d orbital each time the
nuclear charge increases by unity, But the
shielding effect of a d electron is not that
effective, hence the net electrostatic attraction
between the nuclear charge and the outermost
electron increases and the ionic radius
decreases

13. • However the increased nuclear charge is partly
cancelled by the increased screening effect of
electrons in the d – orbitals of penultimate shell.
• When the increased nuclear charge and increased
Screening effect balance each other, the atomic
radii becomes almost constant.
• Increase in atomic radii towards the end may be
attributed to the electron – electron repulsion.
• In fact the pairing of electrons in d – orbitals
occurs after d5 configuration.
• The repulsive interaction between the paired
electron causes Increase in Atomic/ ionic radii

15. • There is increase from the first (3d) to the
second (4d) series of the elements.
• But the radii of the third (5d) series are
virtually the same as 4d
• This is due to the intervention of the 4f orbital
which must be filled before the 5d series of
elements begin.
• There is a steady decrease in atomic radii from
La due to the poor shielding of inner core
electrons (4f) is known lanthanoid contraction.

16. Why do the transition elements exhibit higher
enthalpies of atomisation?
• Because of large number of unpaired electrons
in their atoms they have stronger interatomic
interaction and hence stronger bonding
between atoms resulting in higher enthalpies
of atomisation.

17. IONISATION ENTHALPIES
• Due to an increase in nuclear charge there is an
increase in ionisation enthalpy along each series
of the transition elements from left to right.
• Ionisation enthalpies give some guidance
concerning the relative stabilities of oxidation
states.
• Although the first ionisation enthalpy, in general,
increases, the magnitude of the increase in the
second and third ionisation enthalpies for the
successive elements, in general, is much higher.
• Mostly IE1<IE2 <IE3 in each group

19. • The increase in IE is primarily due to increase
in nuclear charge. As the transition elements
involve the gradual filling of (n-1)d orbitals,
the effect of increase in nuclear charge is
partly cancelled by the increase in screening
effect.
• Consequently, the increase in I.E along the
periods of d – block elements is very small.

20. Relation between I.E and Stability of a
metal in a given oxdn state
• With the help of I.E, we can predict which of
the two metals in a given oxdn state is
thermodynamically more stable.
Eg
• When a metal M (0) is converted into M(II), the
energy required is equal to I1 + I2
Similarly M (IV) = I1 + I2+ I3 + I4

21. • Ni (0) Ni (II) I1 + I2 =2.49 x 103 kJ mol -1
• Pt (0) Pt (II) I1 + I2 =2.66 x 103 kJ mol -1
• Ni (0) Ni (IV)
I1 + I2+ I3 + I4 =11.299 x 103 kJ mol -1
• Pt (0) Pt (IV)
I1 + I2+ I3 + I4 =9.36 x 103 kJ mol -1
I1 + I2 for Ni (II) is less than I1 + I2 for Pt (II). So Ni
(II) is more stable
Similarly Pt (IV) is more stable

22. OXIDATION STATES
+3
• One of the notable features of a transition
element is the great variety of oxidation states it
may show in its compounds
• Stability of a particular oxdn state depends up
on nature of the element with which the
transition metals form the compound

23. • The elements which give the greatest number
of oxidation states occur in or near the middle
of the series. Manganese, for example, exhibits
all the oxidation states from +2 to +7.
• Elements in the beginning of the series exhibit
fewer oxidation state (have small no. of
electrons in which they lose or contribute for
sharing).
• Elements at the end of the series shows fewer
oxdn states because they have too many
electrons in d – orbitals. So they have few
vacant d – orbitals which can be involved in
bonding.

24. • Lower oxdn state – Covalent character
• Higher oxdn state – ionic
• Higher oxdn states are more stable for heavier
members.
Eg : in group VI, Mo (VI) and W (VI) are more stable
than Cr (VI). So Cr (VI) act as strong oxidizing agent.
• The highest oxdn state - +8 (Ruthenium and
Osmium).
• Low oxidation states are found when a complex
compound has ligands capable of π-acceptor
character in addition to the σ-bonding. For example,
in Ni(CO)4 and Fe(CO)5, the oxidation state of nickel
and iron is zero.

25. Trends in Stability of Higher Oxidation
States
• Stability – compounds with F and Oxygen
• The ability of Fluorine to stabilize the highest
oxidation state is due to either high lattice
energy as in case of CoF3 or high bond
enthalpy as in case of VF5 and CrF6.
• The ability of Oxygen to stabilize the highest
oxidation state is due to its ability to form
multiple bonds with metals.

26. Stable halides of first transition elements
Oxdn
no.
4 5 6 7 8 9 10 11 12
+6 Cr F6
+5 VF5 Cr F5
+4 TiX4 VX4
I Cr X4 MNf4
+3 TiX3 VX3 Cr X3 MnF3 Fe X3 Co F3
+2 TiX2
III VX2
I Cr X2 MnX2 Fe X2 Co X2 Ni X2 Cu X2
II ZnX2
+1 Cu XIII
X = F to I, XII = F,
XI = F to Br , X III = Cl to I

27. • The highest oxidation numbers are achieved in
TiX4 (tetrahalides), VF5 and CrF6. The +7 state
for Mn is not represented in simple halides but
MnO3F is known, and beyond Mn, no metal has
a trihalide except FeX3 and CoF3.
• Although V(V)is represented only by VF5, the
other halides, however, undergo hydrolysis to
give oxohalides, VOX3. Another feature of
fluorides is their instability in the low oxidation
states e.g., VX2 (X = CI, Br or I)

28. • All Cu(II) halides are known except the iodide.
In this case, Cu2+ oxidises I– to I2:
2Cu2+ + 4I- → Cu2I2 (s) + I 2
• However, many copper (I) compounds are
unstable in aqueous solution and undergo
disproportionation.
2Cu2+ → Cu2+ + Cu
• The stability of Cu2+ (aq) rather than Cu+(aq) is
due to the much more negative ΔhydH0 of Cu2+
(aq) than Cu+, which more than compensates
for the second ionisation enthalpy of Cu.

29. • Transition metals also exhibits the highest
Oxdn state in their Oxides.
• The ability of Oxygen to stabilize higher
oxidation states are much higher than
Fluorine..
• The highest Oxdn state with Fluorine by Mn is
+4 in MnF4 while it is + 7 in Mn2O7.
• Oxygen has the ability to form Multiple bonds
with Metal atom.
The oxides of 3 – d transition elements are
given below :

30. Ox
dn
No
3 4 5 6 7 8 9 10 11 12
+7 Mn2O7
+6 CrO3
+5 V2O5 MnO2
+4 TiO2 V2O4 CrO2 Mn2O3 Fe2O3
+3 Sc2O3 Ti2O3 V2O3
Cr2O3 Mn3O4 Fe3O4 Co3O4
+2 TiO VO CrO MnO FeO CoO NiO CuO ZnO
+1 Cu2O

31. • The highest oxidation number in the oxides
coincides with the group number and is
attained in Sc2O3 to Mn2O7.
• Beyond Group 7, no higher oxides of Fe above
Fe2O3, are known, although ferrates (VI)
(FeO4)2–, are formed in alkaline media but they
readily decompose to Fe2O3 and O2.
• Besides the oxides, oxocations stabilise V(v) as
VO2
+, V(IV) as VO2+ and Ti(IV) as TiO2+.

32. STANDARD ELECTRODE POTENTIAL
• ELECTRODE POTENTIALS ARE THE
MEASURE OF THE VALUE OF TOTAL
ENTHALPY CHANGE.
• Electrode Potentials value depends
enthalpy of atomization ΔHa & hydration
ΔH hyd
• Lower the std E. P (Eo
red), the more stable
is the oxdn state of the metal in aqueous
state.

34. The E0(M2+/M) value for copper is positive (+0.34V) :
high ΔHa and low ΔH hyd). --- GREATER AMNT OF
ENERGY REQUIRED TO TRANSFORM Cu INTO Cu2+

35. • Due to +ve Eo, Cu does not liberate
hydrogen from acids.
• The general trend towards less negative Eo
values across the series is related to the
general increase in the sum of the first
and second ionisation enthalpies.
• It is interesting to note that the value of Eo
for Mn, Ni and Zn are more negative than
expected from the trend.

36. • The stability of the half-filled d sub-shell in Mn2+
and the completely filled d10 configuration in Zn2+
are related to their Eo values, whereas Eo for Ni is
related to the highest negative ΔhydHo.
• The low value for Sc reflects the stability of Sc3+
which has a noble gas configuration. The highest
value for Zn is due to the removal of an electron
from the stable d10 configuration of Zn2+. The
comparatively high value for Mn shows that
Mn2+(d5) is particularly stable, whereas
comparatively low value for Fe shows the extra
stability of Fe3+ (d5).

37. CHEMICAL REACTIVITY
• Transition metals vary widely in their chemical
reactivity. Many of them are sufficiently
electropositive to dissolve in mineral acids,
although a few are ‘noble’—that is, they are
unaffected by simple acids.
• The metals of the first series with the exception
of copper are relatively more reactive and are
oxidised by 1M H+, though the actual rate at
which these metals react with oxidising agents
like hydrogen ion (H+) is sometimes slow.

38. • The EO valuesfor M2+/M indicate a decreasing
tendency to form divalentcations across the
series.
• This general trend towards less negative EO
values is related to the increase in the sum of
the first and second ionisation enthalpies.
• It is interesting to note that the EO values for
Mn, Ni and Zn are more negative than
expected from the general trend.

39. • EO values for the redox couple M3+/M2+
shows that Mn3+ and Co3+ ions are the
strongest oxidising agents in aqueous
solutions. The ions Ti2+, V2+ and Cr2+ are strong
reducing agents and will liberate hydrogen
from a dilute acid,
e.g.,
• 2 Cr2+(aq) + 2 H+(aq) → 2 Cr3+(aq) + H2(g)

40. MAGNETIC PROPERTIES
• Substances which contain species
(Atoms/ions/molecules) with unpared
electrons in their orbitals – PARAMAGNETIC.
• PARAMAGNETIC SUBSTANCES are weakly
attracted by the magnetic field.
• Strongly attracted called FERROMAGNETIC.
• Substances which do not contain any unpaired
electrons and are repelled by magnetic field -
DIAMAGNETIC.

41. • Transition metals usually contains unpaired
electrons – so it is paramagnetic.
• Paramagnetic behavior increases with
increase in unpaired electron.
• Paramagnetism expressed in terms of
Magnetic moment., it is related to no. of
unpaired electrons.
• The magnetic moments calculated from the
‘spin-only’ formula and those derived
experimentally.
Magnetic moment µ = √ n(n+2) BM

42. n- no. of unpaired electrons
BM – Bohr magnetone (unit of M.M)
BM = 9.27x10-21 erg/gauss
• Single unpaired electronhas a magnetic
moment of 1.73 Bohr magnetons (BM).
• magnetic moment of an electron is due to its
spin angular momentum and orbital angular
momentum

44. Formation of Coloured Ions
• When an electron from a lower energy d
orbital is excited to a higher energy d orbital,
the energy of excitation corresponds to the
frequency of light absorbed.
• This frequency generally lies in the visible
region. The colour observed corresponds to
the complementary colour of the light
absorbed.
• The frequency of the light absorbed is
determined by the nature of the ligand.

45. • Zn 2+ / Cd 2+ - all d orbitals are fully filled
• Ti 4+ - all d orbitals are vacant
so, no d – d transition occurs. Therefore they
do not absorb radiations. So they are
colorless.

46. Formationof Complex Compounds
•Metal ions bind a number of anions or neutral
molecules giving complex
[Fe(CN)6]3–, [Fe(CN)6]4–, [Cu(NH3)4]2+ and
[PtCl4]2–
.
This is due to the
•Comparatively smaller sizes of the metal ions,
• Their high ionic charges and
•The availability of d orbitals for bond formation.

47. Formation of Interstitial Compounds
•When small atoms like H, C or N are trapped
inside the crystal lattices of metals
•They are usually non stoichiometric
•example, TiC, Mn4N, Fe3H, VH0.56 and TiH1.7
(i) They have high melting points, higher than those of
pure metals.
(ii) They are very hard, some borides approach
diamond in hardness.
(iii) They retain metallic conductivity.
(iv) They are chemically inert.

48. Alloy Formation
• Because of similar radii and other characteristics
of transition metals,
• The alloys so formed are hard and have often
high melting points.
• ferrous alloys: chromium, vanadium, tungsten,
molybdenum and manganese are used for the
production of a variety of steels and stainless
steel.
• Alloys of transition metals with non transition
metals such as brass (copper-zinc) and bronze
(copper-tin),

49. CATALYTIC ACTIVITY
• The transition metals and their compounds
are known for their catalytic activity.
• This activity is ascribed to their ability to
adopt multiple oxidation states and to form
complexes.

50. DISPROPORTIONATION
• When a particular oxidation state becomes less
stable relative to other oxidation states, one
lower, one higher, it is said to undergo
disproportionation. For example, manganese (VI)
becomes unstable relative to manganese(VII) and
manganese (IV) in acidic solution.
3 MnVIO4 2– + 4 H+ → 2 MnVIIO–
4 + MnIVO2 + 2H2O

51. Oxides and Oxoanions of Metals
• The elements of first transition series form
variety of oxides of different oxidation states
having general formula MO, M2O3, M3O6,
MO2, MO3.
• Theses oxides are generally formed by heating
the metal with oxygen at high temperature.

52. Sc – Sc2O3 Basic
Ti – TiO Basic, Ti2O2 Basic, TiO2 Amphoteric
V – VO Basic, V2O3 Basic, VO2 Ampho, V2O5 Acidic
Cr – CrO Basic, Cr2O3 Ampho, CrO2 Ampho,
CrO3Acidic
Mn – MnO basic, Mn2O3 Basic, Mn3O4 Ampho,
MnO2 Ampho, Mn2O7 Acidic
Fe – FeO Basic, Fe2O3 Amph, Fe3O4 Basic
Co – CoO Basic
Ni – NiO Basic
Cu – Cu2O Basic, CuO Ampho
Zn – ZnO Ampho

53. • In general
lower oxidation state metal – BASIC
Higher oxidation state metal – ACIDIC
Intermediate oxidation state - AMPHOTERIC
• Example
MnO (+2)basic, Mn2O3 (+3)Basic, Mn3O4 (+
8/3)Ampho,
MnO2 (+4) Ampho, Mn2O7 (+7)Acidic

54. • The highest oxidation number in the oxides
coincides with the group number and is
attained in Sc2O3 to Mn2O7.
• Beyond Group 7, no higher oxides of Fe
above Fe2O3, are known, although ferrates
(VI) (FeO4)2–, are formed in alkaline media
but they readily decompose to Fe2O3 and
O2.
• Besides the oxides, oxocations stabilise
V(v) as VO2
+, V(IV) as VO2+ and Ti(IV) as
TiO2+.

55. • As the oxidation number of a metal increases,
ionic character decreases. In the case of Mn,
Mn2O7 is a covalent green oil. Even CrO3 and
V2O5 have low melting points. In these higher
oxides, the acidic character is predominant.

56. Potassium dichromate K2Cr2O7
STEP 1
• Dichromates are generally prepared from
chromate which in turn are obtained by the
fusion of chromite ore (FeCr2O4) with
sodium or potassium carbonate in free
access of air. The reaction with sodium
carbonate occurs as follows:
4 FeCr2O4 + 8 Na2CO3 + 7 O2 → 8 Na2CrO4+
2Fe2O3 + 8 CO2

57. STEP 2
• The yellow solution of sodium chromate is
filtered and acidified with sulphuric acid to give a
solution from which orange sodium dichromate,
Na2Cr2O7. 2H2O can be crystallised.
2Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O
STEP 3
Conversion of Sodium dichromate in to Potassium
dichromate
Na2Cr2O7 + 2 KCl → K2Cr2O7 + 2 NaCl

58. • The oxidation state of chromiumin chromate
and dichromate is the same.
2 CrO4
2– + 2H+ → Cr2O7
2– + H2O
Cr2O7
2– + 2 OH- → 2 CrO4
2– + H2O
• The chromate ion is tetrahedral whereas the
dichromate ion consists of two tetrahedral
sharing one corner with Cr–O–Cr bond angle
of 126°.

59. •Sodium and potassium dichromates are strong oxidising
agents
Potassium dichromate is used as a primary standard in
volumetric analysis. In acidic solution, its oxidising action
can be represented as follows:
Cr2O7
2– + 14H+ + 6e– → 2Cr3+ + 7H2O (EV = 1.33V)

60. • acidified potassium dichromate will oxidise
iodides to iodine, sulphides to sulphur, tin(II)
to tin(IV) and iron(II) salts to iron(III). The half-
reactions are noted below:
• 6 I– → 3I2 + 6 e– ;
• 3 H2S → 6H+ + 3S + 6e–
• 3 Sn2+ → 3Sn4+ + 6 e–
• 6 Fe2+ → 6Fe3+ + 6 e–
Cr2O7
2– + 14 H+ + 6 Fe2+ → 2 Cr3+ + 6 Fe3+ + 7 H2O

61. Potassium permanganate KMnO4
• Potassium permanganate is prepared by fusion
of MnO2 with an alkali metal hydroxide and an
oxidising agent like KNO3. This produces the
dark green K2MnO4 which disproportionates in
a neutral or acidic solution to give
permanganate.
2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O
3MnO4
2– + 4H+ → 2MnO4
– + MnO2 + 2H2O

62. The manganate and permanganate ions are
tetrahedral; the green manganate is
paramagnetic with one unpaired electron but the
permanganate is diamagnetic.

63. THE INNER TRANSITION ELEMENTS (
f-BLOCK)

64. • The elements in which the additional
electrons enters (n-2)f orbitals are called inner
transition elements. The valence shell
electronic configuration of these elements can
be represented as (n – 2)f0-14(n – 1)d0-1ns2.
• 4f inner transition metals are known as
lanthanides because they come immediately
after lanthanum and 5f inner transition metals
are known as actinoids because they come
immediately after actinium.

65. Electronic Configuration
Element name Symbol Z Ln Ln3+ Radius
Ln3+/ pm
Lanthanum La 57 [Xe]6s25d1 [Xe]4f0 116
Cerium Ce 58 [Xe]4f16s25d1 [Xe]4f1 114
Praesodymium Pr 59 [Xe]4f36s2 [Xe]4f2 113
Neodymium Nd 60 [Xe]4f46s2 [Xe]4f3 111
Promethium Pm 61 [Xe]4f56s2 [Xe]4f4 109
Samarium Sm 62 [Xe]4f66s2 [Xe]4f5 108
Europium Eu 63 [Xe]4f76s2 [Xe]4f6 107
Gadolinium Eu 64 [Xe]4f76s25d1 [Xe]4f7 105
Terbium Tb 65 [Xe] 4f96s2 [Xe]4f8 104
Dysprosium Dy 66 [Xe] 4f106s2 [Xe]4f9 103
Holmium Ho 67 [Xe] 4f116s2 [Xe]4f10 102
Erbium Er 68 [Xe] 4f126s2 [Xe]4f11 100
Thulium Tm 69 [Xe] 4f136s2 [Xe]4f12 99
Ytterbium Yb 70 [Xe] 4f146s2 [Xe]4f13 99
Lutetium Lu 71 [Xe] 4f146s25d1 [Xe]4f14 98

66. Atomic and ionic sizes: The Lanthanide
Contraction
• As the atomic number increases, each
succeeding element contains one more
electron in the 4f orbital and one proton in
the nucleus. The 4f electrons are ineffective in
screening the outer electrons from the
nucleus causing imperfect shielding. As a
result, there is a gradual increase in the
nucleus attraction for the outer electrons.
Consequently gradual decrease in size occur.
This is called lanthanide contraction.

67. Consequences of L. C
• There is close resemblance between 4d and
5d transition series.
• Ionization energy of 5d transition series is
higher than 3d and 4d transition series.
• Difficulty in separation of lanthanides

68. Ionization Enthalpies
• Fairly low I. E
• First ionization enthalpy is around 600 kJ mol-1,
the second about 1200 kJ mol-1 comparable
with those of calcium.
• Due to low I. E, lanthanides have high
electropositive character

69. Coloured ions
• Many of the lanthanoid ions are coloured in
both solid and in solution due to f – f
transition since they have partially filled f –
orbitals.
• Absorption bands are narrow, probably
because of the excitation within f level.
• La3+ and Lu3+ ions do not show any colour
due to vacant and fully filled f- orbitals.

70. Magnetic properties
• The lanthanoid ions other then the f 0 type
(La3+ and Ce3+) and the f14 type (Yb2+ and Lu3+)
are all paramagnetic. The paramagnetism rises
to the maximum in neodymium.
• Lanthanides have very high magnetic
susceptibilities due to their large numbers of
unpaired f-electrons.

71. Oxidation States
• Predominantly +3 oxidation state.
• +3 oxidation state in La, Gd, Lu are especially
stable ( Empty half filled and Completely filled f –
subshell respectively)
• Ce and Tb shows +4 oxdn state ( Ce 4+ - 4fo & Tb4+
4f7)
• Occasionally +2 and +4 ions in solution or in solid
compounds are also obtained.
• This irregularity arises mainly from the extra
stability of empty, half filled or filled f subshell.

72. • The most stable oxidation state of lanthanides
is +3. Hence the ions in +2 oxidation state tend
to change +3 state by loss of electron acting as
reducing agents whereas those in +4 oxidation
state tend to change to +3 oxidation state by
gain of electron acting as a good oxidising
agent in aqueous solution.
• Why Sm2+, Eu2+, and Yb2+ ions in solutions are
good reducing agents but an aqueous solution
of Ce4+ is a good oxidizing agent?

73. properties
• Silvery white soft metals, tarnish in air rapidly
• Hardness increases with increasing atomic
number, samarium being steel hard.
• Good conductor of heat and electricity.
• Promethium - Radioactive

74. Chemical Properties
• Metal combines with hydrogen when gently
heated in the gas.
• The carbides, Ln3C, Ln2C3 and LnC2 are formed
when the metals are heated with carbon.
• They liberate hydrogen from dilute acids and
burn in halogens to form halides.
• They form oxides and hydroxides, M2O3 and
M(OH)3, basic like alkaline earth metal oxides
and hydroxides.

75. Ln
W
ith
acids
With helogensHeated with S
Heated
with
N2
Burn
w
ith
O
2
2
C 2773 K
W
ith
H
O
Ln S2 3
2
32
2LnN LnC Ln(OH) +H
3LnX
HLn O2 3

76. The Actinides
• All isotopes are radioactive, with only 232Th,
235U, 238U and 244Pu having long half-lives.
• Only Th and U occur naturally-both are more
abundant in the earth’s crust than tin.
• The others must be made by nuclear
processes.

77. • The dominant oxidation state of actinides is
+3. Actinides also exhibit an oxidation state of
+4. Some actinides such as uranium,
neptunium and plutonium also exhibit an
oxidation state of +6.
• The actinides show actinide contraction (like
lanthanide contraction) due to poor shielding
of the nuclear charge by 5f electrons.
• All the actinides are radioactive. Actinides are
radioactive in nature.

78. Actinoide Contraction
• The size of atoms / M3+ ions decreases
regularly along actinoid seris. The steady
decrease in ionic/ atomic radii with increase in
atomic number is called Actinoide
Contraction.
• The contraction is greater from element to
element in this series – due to poor shielding
effect by 5 f electron.

79. Electronic configuration
Element name Symbol Z Ln Ln3+ Radius
Ln3+/ pm
Actinium Ac 89 [Rn] 6d17s2 [Rn]4f0 111
Thorium Th 90 [Rn ]5d27s2 [Rn]4f1
Protactinium Pa 91 [Rn]5f26d17s2 [Rn]4f2
Uranium U 92 [Rn]5f36d17s2 [Rn]4f3 103
Neptunium Np 93 [Rn]5f46d17s2 [Rn]4f4 101
Plutonium Pu 94 [Rn]5f67s2 [Rn]4f5 100
Americium Am 95 [Rn]5f77s2 [Rn]4f6 99
Curium Cm 96 [Rn]5f76d17s2 [Rn]4f7 99
Berkelium Bk 97 [Rn]5f97s2 [Rn]4f8 98
Californium Cf 98 [Rn]5f107s2 [Rn]4f9 98
Einsteinium Es 99 [Rn]5f117s2 [Rn]4f10
Fermium Fm 100 [Rn]5f127s2 [Rn]4f11
Mendelevium Md 101 [Rn]5f137s2 [Rn]4f12
Nobelium No 102 [Rn]5f147s2 [Rn]4f13
Lawrencium Lr 103 [Rn]5f146d17s2 [Rn]4f14

80. Magnetic properties
• Paramagnetic behaviour
• Magnetic properties are more complex than
those of lanthanoids.
M.P and B.P
High M.P and B.P
Do not follow regular gradation of M.P or B.P
with increase in atomic number

81. IONISATION ENTHALPY
• Low I.E. so electropositiity is High
COLOUR
• Generally coloured
• Colour depends up on the number of 5 f
electrons
• The ions containing 5 f o and 5 f 7 are
colouress
Eg –
U 3+ (5 f 3 ) – Red
NP 3+ (5 f 4 ) – Bluish

82. THANK YOU