d and f block Elements notes for Class 12th
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- D and f block elements Important questions
A. d block Elements
d block Elements are also called transition elements because of their position between s-block and p-block elements. The d block contains group 3 to 12.
Transition elements are 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 have fully filled d- orbitals in their ground state as well as in their common oxidation states and hence are not regarded as transition elements. ( But Zn, Cd and Hg being end members of transition series are studied along them )
General Electronic Configuration :
D block Elements
Electronic Configuration of First transition Series ( Z= 21 to 30 )
Notes by gtctuition ©
General Properties
1. Atomic Radii : First decreases upto middle of series then increase at the end.
3. M.p and enthalpies of atomization : Due to strong metallic bonding ( which depends upon number of unpaired electrons ) M.p and enthalpies of atomization are high. Zn, Cd and Hg have low m.p because of no unpaired electrons.
Mn has unexpectedly low m.p due to half filled electronic configuration.
4. Ionisation Enthalpies :
# Scandium only shows +3 oxidation state as its electronic configuration is
# Mn shows oxidation states from +2 to +7
# These elements also form compounds in zero oxidation state
6. Standard Electrode Potentials
Standard electrode potential for M(+2)| M represents the tendency to gain electrons by M(+2) ions.
7. Formation of Coloured Ions :
Transition metal ions having unpaired electrons form coloured compounds because they absorb energy from visible light and electrons promoted from one energy level to another in same d- subshell. This is called d-d transitions.
Some colourless ions ( no unpaired electron )
8. Magnetic Properties :
Paramagnetic nature if there are unpaired electrons
Spin magnetic moment is calculated as
Transition elements form complexes due to small size , high nuclear charge and availability of vacant d - orbitals in these elements.
10. Formation of interstitial Compounds :
Because small atoms can easily accomodate spaces b/w transition metal atoms So they form interstitial compounds
11. Alloy formation : Because the atoms of transition metals can substitute atoms of other metals in crystal.
12. Good Catalytic Properties : Because of (i) tendency to form intermediate in suitable reaction.
(ii) Provide large surface for adsorption.
(iii) transition metal ions can change their oxidation state in reaction.
Notes by gtctuition ©
Some Important Compounds ( Potassium dichromate and potassium permanganate )
* Not in syllabus for CBSE 2021 Exams
Potassium dichromate Preparation and Properties
Potassium Permanganate Preparation
B. f - block Elements ( inner transition Elements )
Those elements in which last electron enters to antepenultimate energy level ( n-2)f orbitals.
General Electronic Configuration :
14 Elements Ce(Z= 58) to Lu ( Z= 71).
(ii) Actinoids : Elements following Actinium Ac ( Z= 89 ) and filling of 5f orbitals.
14 Elements Th (Z= 90 ) to Lw ( Z= 103).
* Lanthanum resemble Lanthanoids and Actinium resemble Actinoids So these are included in study of f-block elements.
Lanthanoids
General Electronic configuration:
Electronic configuration of all the lanthanoids :
Chemical Properties of Lanthanoids
Lanthanoid Contraction :
The steady decrease in atomic and ionic radii