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f-block elements exhibit different oxida...

f-block elements exhibit different oxidation state, colour, complex formation like properties. The size oflanthanides decreases due to poor screening effect of 4f electrons. It is called lanthanide contraction. Lanthanide hydroxides are basic in nature
The colour of lanthanide ion is due to

A

`La^(3+) gt Ce^(3+) gt Pm^(3+) gt Yb^(3+)`

B

`Yb^(3+) lt La^(3+) lt Ce^(3+) lt Pm^(3+)`

C

`La^(3+) lt Ce^(3+) lt Pm^(3+) lt Yb^(3+)`

D

`Yb^(3+) lt Pm^(3+) lt La^(3+) lt Ce^(3+)`

Text Solution

Verified by Experts

The correct Answer is:
A
Left to right decreasing order of Ionic radius but not steady decreases
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Knowledge Check

  • (A) Elements of 4f sries are called Lanthanides (R) Lanthanum Belongs to 'f' block

    A
    Both (A) and (R) are true and (R) is the correct explanation of (A)
    B
    Both (A) and (R) are true and (R) is not the correct explanation of (A)
    C
    (A) is true but (R) is false
    D
    Both (A) and (R) are false

  • Regarding lanthanide contraction, some statements are given a) It arises because of the poor shielding effect of 5f-electrons b) The atomic radii and ionic radii steadily decrease from Ce to Lu c) The crystal structures and other properties are similar d) The seperation of lanthanides from one another is difficult from their salt solutions. The correct statements are

    A
    a,b,c
    B
    b,c,d
    C
    a,c,d
    D
    a,b,d

  • On exposure to air, alkali metals get tarnished due to formation of oxides, hydroxides and carbonates on their surface. When heated in air or oxygen they burn vigorously forming different types of oxides depending upon the nature of the metal. The formation and stability of these metals can be explained on the basis of size of alkali metal ion and the anion. Peroxides are colourless, while superoxides are coloured. The normal oxides are basic while peoxides and superoxides act as oxidising agents Na_(2)O_(2) has light yellow colour. This is due to

    A
    Presence of unpaired electron in the moleucle
    B
    Presence of traces of NaO2
    C
    Presence of traces of Na2O
    D
    All

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