8/20/2019 d and f Block Elements Chemistry Class Xii
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Properties Trends Reason
Atomic and
ionic radii
There is a gradual decrease in atomic and ionic radii of
actinoids .
Due to actinoid contraction
Oxidation
states
There is a gradual decrease in atomic and ionic radii of
actinoids. Exhibit mainly +3 oxidation state.
5f , 6d , and 7s subshells are of
comparable energies.
Ionisation
enthalpy
Lower ionisation enthalpies 5f electrons are less
effectively
shielded than 4f electrons.
Magnetic
property
Paramagnetic Presence of unpaired electrons.
Lanthanoid Contraction: The steady decrease in the atomic and
ionic radii of the transition metals as the
atomic number increases is known as lanthanoid contraction. This
is because of filling of 4f orbitals before
the 5d orbitals. This contraction in size is quite
regular.
Actinoid Contraction: The gradual decrease in the ionic radii
with the increase in atomic no. is called
actinoid contraction. It is due to the imperfect shielding of
one 5f electron by the other in the same
subshell.
Topics/ Questions that were asked previously
Variable oxidation states of transition elements (2007,
2008)
Atomic size of transition metals (2012)
Q. There is hardly any increase in atomic size with increasing
atomic number in a series of transition
metals? (2012 Set 3)
Formation of coloured ions by transition metal ions (2007,
2010)
Lanthanoid contraction (2007, 2008, 2009)Oxidation states of
actinoids (2009, 2011, 2012 Set 3)
Q. Actinides exhibit a much larger number of oxidation states
than the lanthanoids? (2012 Set 3)
Q. With the same d -orbital configuration (d 4),
Cr2+ is a reducing agent while Mn 3+ is an oxidizing
agent?
(2012 Set 3)
NCERT questions which have been asked previously
Page Question Number Year
211 Example 8.1 2010
220 Example 8.7 2010
220 Intext question 8.6 2010
232 Intext question 8.10 2009, 2008
234 Exercise-8.7 2007
– 8.11 (ii) 2008
– 8.11 (iii) 2007, 2010
– 8.11 (iv) 2008
– 8.21 (i) 2009, 2012
Best of luck,
Team Meritnation!
Related PostsMastering d- and f-block Elements (Class XII
Chemistry)
Coordination Compounds (Chemistry Class XII)
p-Block Elements (Class XII Chemistry)
Revising Carbon and Its Compounds (Science Class X)
Revising Carbon and Its Compounds (Class X)
IMPORTANT TOPICS for Class XII Chemistry Board Exam: p, d and f
Block elements
Total Comments (8)
1. samar sam | February 11th, 2014 at 8:15 am
Thnks Meritnation…
2. keerthy | December 11th, 2013 at 8:29 pm
thankzz alooot,… it really helped meh..
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8/20/2019 d and f Block Elements Chemistry Class Xii
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3. keerthy | December 11th, 2013 at 8:28 pm
thankzzzz a loooot….. helpd mah a loottt….
4. sirisha | March 24th, 2013 at 10:38 pm
Thank u meritnation team. It’s very helpful to us.
5. rohit | March 10th, 2013 at 8:34 pm
it gave a lot of idea about the questions…which can be
asked,,tnkhs mrn.
6. himanshu | March 10th, 2013 at 5:05 pm
thanks a lot for this great help
7. gopika varma | March 9th, 2013 at 11:40 pm
thanks alot meritnation team……..gr8 help
8. PRIYANKA PALIWAL | March 9th, 2013 at 2:34 pm
thanks meritnation
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