590 Chapter 12 The f-Block Elements and their Properties
12.3 | COMPARISON BETWEEN LANTHANOIDS AND ACTINOIDS
Similarities
1. Both are electropositive and strongly reducing in nature.
2. Both have stable oxidation state of +3.
3. Ions of both series are coloured due to f–f transition.
4. Both series show a gradual decrease in ionic radii.
Differences
The differences are tabulated in Table 12.5.
Table 12.5 Lanthanoids vs actinoids
Lanthanoids Actinoids
1. Apart from +3 oxidation state, +2 and +4 are 1. Apart from +3 oxidation state, +4, +5, +6 and +7 are
available for some of the elements. available for some of the elements.
2. All elements are non-radioactive except Pm. 2. All elements are radioactive.
3. Lanthanoid contraction is less than actinoid 3. Actinoid contraction is more than lanthanoid
contraction. contraction.
4. Lanthanoids have lesser tendency towards complex 4. Actinoids have relatively stronger tendency towards
formation. complex formation.
5. Oxides and hydroxides are relatively less basic. 5. Oxides and hydroxides are more basic.
6. Elements have less density. 6. Elements have relatively more density.
| SINGLE CORRECT CHOICE TYPE QUESTIONS
1. Colour of La2+ is due to 5. Which of the following properties varies between
(A) d–d transition. lanthanoids and actinoids?
(B) f–f transition. (A) Highest oxidation state.
(C) charge transfer. (B) Radioactive nature.
(D) None of these. (C) Basicity of hydroxides.
2. The colour of Nd3+ (At no. 60) will be similar to (D) All of these.
(A) Ho3+ (At. no. 67). 6. Which of the following elements is used in the
(B) Gd3+ (At. no. 64). treatment of cancer?
(C) Er3+ (At. no. 68). (A) Uranium (B) Thorium
(D) Yb2+ (At. no. 70). (C) Cerium (D) Plutonium
3. Choose the correct order of ionic radius from the given 7. Which of the following species is not paramagnetic?
options (where atomic numbers of Ce, Pr, Eu and Dy (A) Yb2+ (At. no. 70)
are 58, 59, 63, and 66, respectively) (B) Ce4+ (At. no. 58)
(A) Ce3+ > Pr3+ > Dy3+ > Eu3+ (C) Lu3+ (At. no. 71)
(B) Pr3+ > Dy3+ > Eu3+ > Ce3+ (D) All of these.
(C) Dy3+ > Eu3+ > Ce3+ > Pr3+ 8. Calculate the Zeffective for the f-electron in Ce3+.
(D) Ce3+ > Pr3+ > Eu3+ > Dy3+ (A) 54 (B) 5 (C) 4 (D) 3
4. Which of following characteristics is not the point of 9. Tb 4+ (At. no. 65) is stable because
resemblance between lanthanoids and actinoids? (A) it has noble gas configuration.
(A) Reducing property. (B) it has half-filled electronic configuration of f-orbitals.
(B) Oxidation state of +3. (C) it has fully-filled electronic configuration of d-orbitals.
(C) Trends of ionic radii for M3+ ions. (D) it has fully-filled electronic configuration of f-orbitals.
(D) Tendency towards complex formation. 10. Actinoid contraction is more compared to lantha-
noid contraction because
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Answers 591
(A) 5f orbitals are more diffused as compared to 16. The magnetic moment of Am5+ (At. no. 95) is
4f-orbital from nucleus. (A) 24 BM (B) 35 BM
(B) 4f-orbitals are more diffused as compared to
(C) 15 BM (D) 3 BM
5f-orbitals.
(C) Shielding effect of electrons present in 4f- and 17. Which of the following elements is not an f-block
5f-orbitals is equal. element?
(D) The azimuthal quantum numbers of 4f- and 5f- (A) No (B) Nd (C) Nb (D) Np
orbitals are the same.
18. On moving from Ce3+ to Lu3+, the cation having max-
11. Which of the following cations has the strongest imum number of unpaired electrons is
tendency towards complex formation? (A) Ce3+ (B) Lu3+ (C) Eu3+ (D) Gd3+
(A) Sm3+ (B) Lu3+ (C) Gd3+ (D) Yb3+
19. Lanthanoid from series is
12. Which of the following elements has maximum
composition in Misch metal, which is used in gas (A) La to Lu
lighters? (B) Th to Lr
(A) La (B) Fe (C) Ce (D) Other metals (C) Ce to Lu
13. Which of the following Ce compound is used for (D) Ac to Lr
making crucibles? 20. Which of the following statements is true for
(A) CeO2 (B) CeS (C) ThO2 (D) Nd2O3 f-block elements?
14. The gradual decrease in radius for lanthanoid ele- (A) They can have electrons from f 0 to f 14.
ments is not obeyed by (B) Group number is 3 in the periodic table.
(A) Eu only (B) Yb only (C) With the increase in number of f-electrons, the
(C) Both Eu and Yb (D) None radius decreases due to poor shielding effect of
15. The gradual decrease in radius of M3+ ion for lantha- f-electrons.
noids is not obeyed by (D) All of these.
(A) Eu only (B) Yb only
(C) Both Eu and Yb (D) None of these
| ANSWERS
Single Correct Choice Type Questions
1. (A) 6. (B) 11. (B) 16. (A)
2. (C) 7. (D) 12. (C) 17. (C)
3. (D) 8. (C) 13. (B) 18. (D)
4. (D) 9. (B) 14. (C) 19. (C)
5. (D) 10. (A) 15. (D) 20. (D)
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