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CBSE Class 12 · 2011 · All India · d and f Block ElementsVery Short Answer

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What is meant by 'lanthanoid contraction'?

Answer: The steady decrease of atomic/ionic radii across La→Lu, due to poor shielding by 4f electrons.

Solution

The regular decrease in the atomic and the trivalent ionic radii of the lanthanoids with increasing atomic number (La → Lu) is called the lanthanoid contraction.
Cause: the 4f electrons shield the increasing nuclear charge imperfectly, so the outer shells are pulled steadily inward.

CBSE Class 12 Board · 2011 · All India · Subjective

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More board questions on d and f Block Elements

  1. Transition metals are known to form interstitial compounds. The formation of interstitial compounds makes the transition metal:
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  2. Assertion (A): Zr and Hf have almost similar atomic radii.
    Reason (R): This is due to lanthanoid contraction.
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  3. Which of the following ions has the electronic configuration 3d? (Atomic numbers: Mn = 25, Co = 27, Ni = 28)
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  4. Which property of transition metals enables them to behave as catalysts?
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  5. (a) A transition element X has the electronic configuration [Ar]4s²3d³. Predict its likely oxidation states.
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  6. a) Write any two consequences of lanthanoid contraction.
    b) Name the element of the 3d series which exhibits the largest number of oxidation states. Give a reason.
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