CBSE Class 12 Chemistry The d and f Block Elements Notes and Questions

14. Most of transition elements are used as catalyst. )t is due to [i] partially filled [n‐1]orbital [ii]Variable oxidation state [iii] Ability to change oxidation state frequently.

15. Most of transition elements form coloured compounds due to presence of unpaired electrons in[n‐1] d orbital & thus they can undergo d‐d transition.

16. Most of transition elements form complex compounds due to [i]small size [ii] high charge[iii] presence of vacant d‐orbital of suitable energy.

17. Transition elements have lower value of Reduction Potential due to high ionization potential, high heat of sublimation & low enthalpy of hydration.

18. Transition elements form interstitial compounds because size of interstitial voids is similar tosize of non‐ metals C, N, O, i.

19. Transition elements form alloys due to similar ionic radii.

20. The oxides of transition metals in lower oxidation state are BAS)C, intermediate oxidation state are AMP(OTER)C, highest oxidation state are ACiDiC.

LANTHANOIDS: ‐‐‐

1. The 14 elements after Lanthanum having atomic number 58 to71 are collectively known as Lanthanoids.
2. The general electronic configuration of these elements is 

3. Most common oxidation state of these elements is +3, but Ce shows +4, Eu +2, because they acquire stable configuration.

4. The size of Lanthanoids and its trivalent ion decreases from La to Lu due to poor shielding of 4f electrons. )t is known as lanthanoids contraction.

ACTINOIDS:1.

The 14 elements after Actinium having atomic number 90 to 113 are collectively known as Actinoids.

Important Questions for NCERT Class 12 Chemistry The d and f Block Elements

Question. General electronic configuration of lanthanides is
(a) (n – 2) f^{1 – 14} (n – 1) s²p⁶d^{0 – 1} ns²
(b) (n – 2) f^{10 – 14} (n – 1) d^{0 – 1} ns²
(c) (n – 2) f ^{0 – 14} (n – 1) d¹⁰ ns²
(d) (n – 2) d^{0 – 1} (n – 1) f^{1 – 14} ns² 
Answer    B

Question. Which of the following statement is not correct?
(a) La(OH)₃ is less basic than Lu(OH)₃.
(b) In lanthanide series ionic radius of Ln⁺³ ion decreases.
(c) La is actually an element of transition series rather lanthanides.
(d) Atomic radius of Zn and Hf are same because of lanthanide contraction.

Answer    A

Question. The lanthanide contraction is responsible for the fact that
(a) Zr and Hf have about the same radius
(b) Zr and Zn have the same oxidation state
(c) Zr and Y have about the same radius
(d) Zr and Nb have similar oxidation state. 

Answer    A

Question. Which of the following statements concerning lanthanide elements is false?
(a) All lanthanides are highly dense metals.
(b) More characteristic oxidation state of lanthanide elements is +3.
(c) Lanthanides are separated from one another by ion exchange method.
(d) Ionic radii of trivalent lanthanides steadily increases with increase in the atomic number.

Answer    D

Question. The reason for greater range of oxidation states in actinoids is attributed to
(a) actinoid contraction
(b) 5f, 6d and 7s levels having comparable energies
(c) 4f and 5d levels being close in energies
(d) the radioactive nature of actinoids.

Answer    B

Question. Which of the following exhibits only +3 oxidation state?
(a) U
(b) Th
(c) Ac
(d) Pa 

Answer    C

Question. The chief ore of Hg is: 
(a) Pyrolusite
(b) Bauxite
(c) Galena
(d) Cinnabar

Question. The transition element which shows the highest oxidation state is: 
(a) Iron
(b) Vanadium
(c) Manganese
(d) Chromium

Question. Gun metal is: 
(a) Cu + Zn
(b) Cu + Sn + Zn
(c) Cu + Sn
(d) Zn + Sn

Question. Transition elements form coloured ions due to :
(a) d-d transition 
(b) fully filled d-orbitals
(c) smaller atomic radii
(d) availability of s-electrons

Question. CuSO₄ and KCN react to produce : 
(a) CuCN₂
(b) CuCN
(c) K₃[Cu(CN)₄]
(d) K₄[Cu(CN)₆ ]

Question. Which of the following is greatest paramagnetic?
(a) Cu+
(b) Fe2+ 
(c) Fe3+
(d) Cu2+

Question. The Mohr’s salt is shown by: 
(a) FeSO₄ (NH₄)₂SO₄.6H₂O
(b) FeSO₄ (NH₃)2SO4.6H₂O
(c) K2SO₄Al₂ (SO₄ )3.24H₂O
(d) FeSO₃(NH₂ )4SO₄.6H₂O

Question. German silver is an alloy of: 
(a) Fe, Cr, Ni
(b) Ag, Cu Au
(c) Cu, Zn, Ni
(d) Cu, Zn, Sn

Question. The composition of duralumin is :
(a) Al 94%, Mg 6%
(b) Cu 56%, Zn 24%, Ni 20%
(c) Cu 95%, Al 5%
(d) Al 95%, Cu 4%, Mn 0.5%, Mg 0.5%

Question. The number of water molecules in Mohr's salt is :
(a) 2
(b) 4
(c) 6
(d) 8

Question. Philosopher's wool on heating with BaO at 1100°C produces : 
(a) Ba + ZnCl₂
(b) BaCdO₂
(c) BaZnO₂
(d) BaO2 + Zn

Question. Which of the following is not an ore of iron?
(a) limonite
(b) casiterite 
(c) magnetite
(d) none of these

Question. The colourless species is : 
(a) VCl₃
(b) VOSO₄
(c) Na₃VO₄
(d) [V(H₂O)₆]SO₄. H₂O

Question. Lanthanide for which +II and +III oxidation states are common is : 
(a) La
(b) Pr
(c) Ce
(d) Eu 

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