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d – AND f – BLOCK ELEMENTS
TINTO JOHNS M. Sc., M. Ed
• The d-block of the periodic table contains the
elements of the groups 3-12 in which the d
orbitals are progressively fil...
• A transition element is defined as
the one which has incompletely
filled d orbitals in its ground state
or in any one of...
Position in the Position in the Periodic Table Periodic
Table
• The d–block occupies the large middle section
flanked by s...
Physical properties
• The transition metals (with the exception of
Zn, Cd and Hg) are very much hard and have
low volatili...
MELTING POINT AND BOILING POINT
• High M.P and B.P - Due to strong metallic bond
and the presence of half filled d- orbita...
• In moving along the period from left to right,
the M.P of these metals first INCREASES to
MAXIMUM and the DECREASES regu...
• melting points of these metals rise to a maximum at
d5 except for anomalous values of Mn and Tc and fall
regularly as th...
Trends in enthalpies of atomization of transition elements
1. Greater the number of valence electrons, stronger the
inter ...
Atomic and ionic radii
• The Atomic/ionic radii first DECREASES till the
middle, becomes almost constant and then
INCREASE...
• However the increased nuclear charge is partly
cancelled by the increased screening effect of
electrons in the d – orbit...
• There is increase from the first (3d) to the
second (4d) series of the elements.
• But the radii of the third (5d) serie...
Why do the transition elements exhibit higher
enthalpies of atomisation?
• Because of large number of unpaired electrons
i...
IONISATION ENTHALPIES
• Due to an increase in nuclear charge there is an
increase in ionisation enthalpy along each series...
• The increase in IE is primarily due to increase
in nuclear charge. As the transition elements
involve the gradual fillin...
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 tw...
• 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...
OXIDATION STATES
+3
• One of the notable features of a transition
element is the great variety of oxidation states it
may ...
• The elements which give the greatest number
of oxidation states occur in or near the middle
of the series. Manganese, fo...
• Lower oxdn state – Covalent character
• Higher oxdn state – ionic
• Higher oxdn states are more stable for heavier
membe...
Trends in Stability of Higher Oxidation
States
• Stability – compounds with F and Oxygen
• The ability of Fluorine to stab...
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
+...
• The highest oxidation numbers are achieved in
TiX4 (tetrahalides), VF5 and CrF6. The +7 state
for Mn is not represented ...
• All Cu(II) halides are known except the iodide.
In this case, Cu2+ oxidises I– to I2:
2Cu2+ + 4I- → Cu2I2 (s) + I 2
• Ho...
• Transition metals also exhibits the highest
Oxdn state in their Oxides.
• The ability of Oxygen to stabilize higher
oxid...
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 Mn3O...
• The highest oxidation number in the oxides
coincides with the group number and is
attained in Sc2O3 to Mn2O7.
• Beyond G...
STANDARD ELECTRODE POTENTIAL
• ELECTRODE POTENTIALS ARE THE
MEASURE OF THE VALUE OF TOTAL
ENTHALPY CHANGE.
• Electrode Pot...
The E0(M2+/M) value for copper is positive (+0.34V) :
high ΔHa and low ΔH hyd). --- GREATER AMNT OF
ENERGY REQUIRED TO TRA...
• Due to +ve Eo, Cu does not liberate
hydrogen from acids.
• The general trend towards less negative Eo
values across the ...
• The stability of the half-filled d sub-shell in Mn2+
and the completely filled d10 configuration in Zn2+
are related to ...
CHEMICAL REACTIVITY
• Transition metals vary widely in their chemical
reactivity. Many of them are sufficiently
electropos...
• The EO valuesfor M2+/M indicate a decreasing
tendency to form divalentcations across the
series.
• This general trend to...
• EO values for the redox couple M3+/M2+
shows that Mn3+ and Co3+ ions are the
strongest oxidising agents in aqueous
solut...
MAGNETIC PROPERTIES
• Substances which contain species
(Atoms/ions/molecules) with unpared
electrons in their orbitals – P...
• Transition metals usually contains unpaired
electrons – so it is paramagnetic.
• Paramagnetic behavior increases with
in...
n- no. of unpaired electrons
BM – Bohr magnetone (unit of M.M)
BM = 9.27x10-21 erg/gauss
• Single unpaired electronhas a m...
Formation of Coloured Ions
• When an electron from a lower energy d
orbital is excited to a higher energy d orbital,
the e...
• Zn 2+ / Cd 2+ - all d orbitals are fully filled
• Ti 4+ - all d orbitals are vacant
so, no d – d transition occurs. Ther...
Formationof Complex Compounds
•Metal ions bind a number of anions or neutral
molecules giving complex
[Fe(CN)6]3–, [Fe(CN)...
Formation of Interstitial Compounds
•When small atoms like H, C or N are trapped
inside the crystal lattices of metals
•Th...
Alloy Formation
• Because of similar radii and other characteristics
of transition metals,
• The alloys so formed are hard...
CATALYTIC ACTIVITY
• The transition metals and their compounds
are known for their catalytic activity.
• This activity is ...
DISPROPORTIONATION
• When a particular oxidation state becomes less
stable relative to other oxidation states, one
lower, ...
Oxides and Oxoanions of Metals
• The elements of first transition series form
variety of oxides of different oxidation sta...
Sc – Sc2O3 Basic
Ti – TiO Basic, Ti2O2 Basic, TiO2 Amphoteric
V – VO Basic, V2O3 Basic, VO2 Ampho, V2O5 Acidic
Cr – CrO Ba...
• In general
lower oxidation state metal – BASIC
Higher oxidation state metal – ACIDIC
Intermediate oxidation state - AMPH...
• The highest oxidation number in the oxides
coincides with the group number and is
attained in Sc2O3 to Mn2O7.
• Beyond G...
• As the oxidation number of a metal increases,
ionic character decreases. In the case of Mn,
Mn2O7 is a covalent green oi...
Potassium dichromate K2Cr2O7
STEP 1
• Dichromates are generally prepared from
chromate which in turn are obtained by the
f...
STEP 2
• The yellow solution of sodium chromate is
filtered and acidified with sulphuric acid to give a
solution from whic...
• The oxidation state of chromiumin chromate
and dichromate is the same.
2 CrO4
2– + 2H+ → Cr2O7
2– + H2O
Cr2O7
2– + 2 OH-...
•Sodium and potassium dichromates are strong oxidising
agents
Potassium dichromate is used as a primary standard in
volume...
• acidified potassium dichromate will oxidise
iodides to iodine, sulphides to sulphur, tin(II)
to tin(IV) and iron(II) sal...
Potassium permanganate KMnO4
• Potassium permanganate is prepared by fusion
of MnO2 with an alkali metal hydroxide and an
...
The manganate and permanganate ions are
tetrahedral; the green manganate is
paramagnetic with one unpaired electron but th...
THE INNER TRANSITION ELEMENTS (
f-BLOCK)
• The elements in which the additional
electrons enters (n-2)f orbitals are called inner
transition elements. The valence ...
Electronic Configuration
Element name Symbol Z Ln Ln3+ Radius
Ln3+/ pm
Lanthanum La 57 [Xe]6s25d1 [Xe]4f0 116
Cerium Ce 58...
Atomic and ionic sizes: The Lanthanide
Contraction
• As the atomic number increases, each
succeeding element contains one ...
Consequences of L. C
• There is close resemblance between 4d and
5d transition series.
• Ionization energy of 5d transitio...
Ionization Enthalpies
• Fairly low I. E
• First ionization enthalpy is around 600 kJ mol-1,
the second about 1200 kJ mol-1...
Coloured ions
• Many of the lanthanoid ions are coloured in
both solid and in solution due to f – f
transition since they ...
Magnetic properties
• The lanthanoid ions other then the f 0 type
(La3+ and Ce3+) and the f14 type (Yb2+ and Lu3+)
are all...
Oxidation States
• Predominantly +3 oxidation state.
• +3 oxidation state in La, Gd, Lu are especially
stable ( Empty half...
• The most stable oxidation state of lanthanides
is +3. Hence the ions in +2 oxidation state tend
to change +3 state by lo...
properties
• Silvery white soft metals, tarnish in air rapidly
• Hardness increases with increasing atomic
number, samariu...
Chemical Properties
• Metal combines with hydrogen when gently
heated in the gas.
• The carbides, Ln3C, Ln2C3 and LnC2 are...
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) ...
The Actinides
• All isotopes are radioactive, with only 232Th,
235U, 238U and 244Pu having long half-lives.
• Only Th and ...
• The dominant oxidation state of actinides is
+3. Actinides also exhibit an oxidation state of
+4. Some actinides such as...
Actinoide Contraction
• The size of atoms / M3+ ions decreases
regularly along actinoid seris. The steady
decrease in ioni...
Electronic configuration
Element name Symbol Z Ln Ln3+ Radius
Ln3+/ pm
Actinium Ac 89 [Rn] 6d17s2 [Rn]4f0 111
Thorium Th 9...
Magnetic properties
• Paramagnetic behaviour
• Magnetic properties are more complex than
those of lanthanoids.
M.P and B.P...
IONISATION ENTHALPY
• Low I.E. so electropositiity is High
COLOUR
• Generally coloured
• Colour depends up on the number o...
THANK YOU
d and f block elements  XII (LATEST)
d and f block elements  XII (LATEST)
d and f block elements  XII (LATEST)
d and f block elements  XII (LATEST)
d and f block elements  XII (LATEST)
d and f block elements  XII (LATEST)
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d and f block elements XII (LATEST)

CBSE CHEMISTRY d AND f BLOCK ELEMENTS, CBSE 12 CHEMISTRY

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d and f block elements XII (LATEST)

  1. 1. d – AND f – BLOCK ELEMENTS TINTO JOHNS M. Sc., M. Ed
  2. 2. • 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.
  3. 3. • 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
  4. 4. 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.
  5. 5. 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.
  6. 6. 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
  7. 7. • 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.
  8. 8. • 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
  9. 9. 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
  10. 10. 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
  11. 11. • 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
  12. 12. • 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.
  13. 13. 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.
  14. 14. 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
  15. 15. • 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.
  16. 16. 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
  17. 17. • 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
  18. 18. 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
  19. 19. • 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.
  20. 20. • 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.
  21. 21. 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.
  22. 22. 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
  23. 23. • 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)
  24. 24. • 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.
  25. 25. • 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 :
  26. 26. 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
  27. 27. • 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+.
  28. 28. 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.
  29. 29. 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+
  30. 30. • 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.
  31. 31. • 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).
  32. 32. 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.
  33. 33. • 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.
  34. 34. • 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)
  35. 35. 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.
  36. 36. • 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
  37. 37. 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
  38. 38. 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.
  39. 39. • 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.
  40. 40. 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.
  41. 41. 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.
  42. 42. 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),
  43. 43. 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.
  44. 44. 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
  45. 45. 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.
  46. 46. 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
  47. 47. • 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
  48. 48. • 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+.
  49. 49. • 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.
  50. 50. 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
  51. 51. 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
  52. 52. • 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°.
  53. 53. •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)
  54. 54. • 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
  55. 55. 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
  56. 56. The manganate and permanganate ions are tetrahedral; the green manganate is paramagnetic with one unpaired electron but the permanganate is diamagnetic.
  57. 57. THE INNER TRANSITION ELEMENTS ( f-BLOCK)
  58. 58. • 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.
  59. 59. 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
  60. 60. 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.
  61. 61. 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
  62. 62. 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
  63. 63. 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.
  64. 64. 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.
  65. 65. 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.
  66. 66. • 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?
  67. 67. 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
  68. 68. 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.
  69. 69. 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
  70. 70. 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.
  71. 71. • 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.
  72. 72. 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.
  73. 73. 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
  74. 74. 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
  75. 75. 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
  76. 76. THANK YOU

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