Introduction, position in periodic table, transition elements & inner transition elements, lanthanoids & actinoids, General trends in properties, atomic radii, atomic volume, melting points, boiling points, density, standard electrode potentials, oxidation states, Some practice questions.

1. d- and f- BLOCK ELEMENTS
(PART : 1)
Prepared by:
ARUNESH GUPTA
PGT (CHEMISTRY), KV BARRACKPORE (AFS)

3. The d block elements
Group 3 4 5 6 7 8 9 10 11 12
Period 4 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn
Period 5 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd
Period 6 57La 72Hf 73Ta 74W 75Re 76Os 77Ir 78Pt 79Au 80Hg
Period 7 89Ac 104Rf 105Db 106Sg 107Bh 108Hs 109Mt 110Ds 111Rg 112Cn

4. Group 3 4 5 6 7 8 9 10 11 12
Atomic no. 21 22 23 24 25 26 27 28 29 30
Element Sc Ti V Cr Mn Fe Co Ni Cu Zn
Electronic
configuration
3d14s2 3d24s2 3d34s2 3d54s1 3d54s2 3d64s2 3d74s2 3d84s2 3d104s1 3d104s2
1st Transition series (3d Series) Sc to Zn
2nd Transition Series
Second (4d) d-block Series (Y–Cd)
Atomic no. 39 40 41 42 43 44 45 46 47 48
Element Y Zr Nb Mo Tc Ru Rh Pd Ag Cd
Electronic
configuration
4d15s2 4d25s2 4d45s1 4d55s1 4d55s2 4d75s1 4d85s1 4d10 4d105s1 4d105s2

5. Third (5d) d-block Series (La–Hg)
Atomic no. 57 72 73 74 75 76 77 78 79 80
Element La Hf Ta W Re Os Ir Pt Au Hg
Electronic
configuration
5d16s2 5d26s2 5d36s2 5d46s2 5d56s2 5d66s2 5d76s2 5d96s1 5d106s1 5d106s2
Fourth (6d) d-block Series (Ac–Cn)
Atomic no. 89 104 105 106 107 108 109 110 111 112
Element Ac Rf (Unq) Db (Unp)
Sg
(Unh)
Bh (Uns) Hs (Uno) Mt (Une) Ds (Uun) Rg (Uuu) Cn (Uub)
Electronic
configuration
6d17
s2
6d27s2 6d37s2 6d47s2 6d57s2 6d67s2 6d77s2 6d87s2 6d97s2 6d107s2

6. The elements lying in the middle of periodic table belonging to groups 3 to 12 are
known as
d – block elements or transition elements which lie between s block & p block
elements.
General electronic configuration of d block elements: (n-1) d0-10 ns0-2.
1st Transition series: Sc (21) to Zn (30) - 3d series
2nd Transition series : Y (39) to Cd (48) - 4d series
3rd Transition series: La (57) to Hg (80) - 5d series
4th Transition series: Ac (89) to Uub (112) - 6d series
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, mercury are not regarded as transition metals due to completely
filled d – orbital. (n-1) d10
Intext question: Silver atom has completely filled d orbitals (4d10) in its ground state. How can
we say that it is a transition state?

7. The f-Block elements: 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.
These are called inner transition series. These lie in Group 3 in a periodic
table.
Lanthanoids: The 14 elements immediately following lanthanum, i.e.,
Cerium Ce (58) to Lutetium Lu (71) are called lanthanoids. They belong to
first inner transition series in 4f series.
Lanthanum (57) has similar properties. Therefore, it is studied along with
lanthanoids.
Actinoids: The 14 elements immediately following actinium (89), with
atomic numbers Th - 90 (Thorium) to Lr - 103 (Lawrencium) are called
actinoids. They belong to second inner transition series in 5f series.

8. Physical properties:
# Typical metallic properties of d block elements are
density, high tensile strength, ductility, malleability, high
thermal, electrical conductivity and metallic lustre.

9. 1. Atomic Radii:
(i) The atomic radii of the transition metals lie in-between those of s- and p-block elements.
(ii) Generally the atomic radii of d-block elements in a series decrease with increase in atomic
number but the decrease in atomic size is small after midway.
Explanation The atomic radius decreases with the increase in atomic number as the nuclear charge
increases whereas the shielding effect of d-electron is small. After midway, as the electrons enter
the last but one (penultimate) shell, the added d-electron shields (screens) the outermost electron.
Hence, with the increase in the d-electrons, screening effect increases. This counterbalances the
increased nuclear charge due to increase in atomic number. As a result, the atomic radii remain
practically same after chromium. For example in Fe, the two opposing tendencies almost
counterbalance and there is no change in the size from Mn to Fe.
(iii) At the end of the period, there is a slight increase in the atomic radii.
Explanation Near the end of series, the increased electron-electron repulsions between added
electrons in the same orbitals are greater than the attractive forces due to the increased nuclear
charge. This results in the expansion of the electron cloud and thus the atomic radius increases.
(iv) The atomic radii increase down the group. This means that the atomic radii of second series are
larger than those of first transition series. But the atomic radii of the second and third transition
series are almost the same. Explanation: The atomic radii of the elements of the second and third
transition metals are nearly same due to lanthanide contraction (or also called lanthanoid
contraction) discussed later.

11. Melting points & boiling points of transition
elements
• High melting points of transition elements is due to
greater no. of electrons in (n-1) d orbitals, have strong
metallic bond with the increase in no. of unpaired
electrons.
• As shown in the graph m.p. increases & then
decreases from Sc to Zn.
• Mn & Tc have comparatively low melting points, due to
exceptionally stable (n–1) d5 ns2, half filled electronic
configuration.
• e,g. Cr has maximum m.p. (3d5 4s1) and Zn has least
m.p. (3d10 4s2) for first transition series.
• The same trends is observed for 2nd & 3rd transition
elements (4d & 5d series)
• Tungsten has the highest m.P. (3410oc).
• Mercury is liquid at room temperature (m.P. – 38.9°C)
due to absence of unpaired electrons, and weak
metallic bonding.

12. Trends in boiling points of d- block elements

13. Trends in Boiling points of transition metal
series
This trend is same as that of m.p. trends, depends on no. of electrons as
unpaired electrons & strength of metallic bond.
The enthalpy of atomisation increases generally from Sc to Cu. Zn is the
exception.
The density of transition metals increases from Sc to Cu with
exception to Zn.
Density =
𝑴𝒂𝒔𝒔
𝑽𝒐𝒍𝒖𝒎𝒆
.
With the increase in At. No. mass increases but atomic radii or
volume correspondingly decreases & hence density increases.

14. Trends in atomic radii of transition elements

15. Atomic radii: The atomic radii decrease from Sc to Cr because the
effective nuclear charge increases. The atomic size of Fe, Co, Ni is
almost same because the attraction due to increase in nuclear
charge is cancelled by the repulsion because of increase in
shielding effect. Cu and Zn have bigger size because the shielding
effect increases and electron - electron repulsions increases.
Due to Lanthanoid contraction, the atomic radii of 2nd & 3rd transition series
are nearly same.
Zr of 2nd transition series & Hf of 3rd transition series have nearly same atomic
radii.

16. Density:
d-block elements have high density because of their small
atomic size and strong metallic bonding.
# Osmium has slightly lower density (22.52 g cm-3) as
compared to iridium (22.61 g cm-1).
Densit
y
Sc Ti V Cr Mn Fe Co Ni Cu Zn
g/cm3 3.0 4.54 6.12 7.19 7.40 7.87 8.74 8.90 8.92 7.13
Reactivity:
d-block elements are less reactive due to high ionisation
energies. Some are almost inert and known as noble metals,
e.g., Au; Pt, Os, Ir, etc

17. OXIDATION STATES
Oxidation states: Transition metals show variable oxidation
states due to tendency of (n-1)d as well as ns electrons to take
part in bond formation.

18. Trends in M2+/M Standard Electrode
Potentials
Group 3 4 5 6 7 8 9 10 11 12
Element Sc Ti V Cr Mn Fe Co Ni Cu Zn
E°M
2+
/ M in V - -1.63 -1.18 -0.90 -1.18 -0.44 -0.28 -0.25 +0.34 -0.76
(i) There is no general trends in standard reduction
potential values of 1st Transition elements.
Explanation: This is due to irregular trends in the
values of ΔaH° and sum of 1st and 2nd ionisation
enthalpy values from Sc to Zn.
(ii) The Eɵ
Cu2+/Cu value is +0.34V. This is due to high
ΔaH° and low ΔhydH°.
(iii) Eɵ
Mn2+/Mn value of Mn does not follow the regular
trend due to its half filled d5 configuration.

19. RECAPITULATION:
• (I) What is the general configuration of d- block & f- block elements?
• (Ii) What is the position of f – block elements in the periodic table?
• (Iii) Why are f - block elements called inner transition elements ?
• (iv) Why are Zn, Cd & Hg not true transition elements?
• (v) How does the M.P. And B.P. of 1st transition series vary?
• (vii) Why does transition elements have high enthalpy of atomization?
• (viii) Name the element of 1st transition metal which does not exhibit the
variable oxidation state.

20. HOME ASSIGNMENT
(i) What is the general configuration of d- block & f- block elements?
(ii) What is the position of f – block elements in the periodic table?
(iii) Why are f - block elements called inner transition elements ?
(iv) Why are Zn, Cd & Hg not true transition elements?
(v) How does the melting points and boiling points of 1st transition series vary?
(vi) Why does transition elements have high enthalpy of atomization?
(vii) Silver atom has completely filled d orbitals (4d10) in its ground state. How is silver a transition element?
(vii) Why Mn & Tc show anomalous behavior in melting point?
(viii) Atomic radii of 1st transition elements first decreases, it remains nearly same & finally increases. Why?
(ix) 2nd & 3rd transition elements have nearly same atomic radii. Why?
(x) Zr (160pm) & Hf (59pm) have nearly same atomic radii. Why?
(xi) Name the element of 1st transition metal which does not exhibit the variable oxidation state.
(xii) Which of the 3d series of the transition metals exhibit the largest number of oxidation states & why?
(xiii) Why is Cr2+ reducing whereas Mn3+ is oxidizing when both have d4 configuration?
(Xiv) Why is the highest oxidation state of a metal exhibited by a metal in its oxide or fluoride only?