JEE Chemistry The D and F Block Elements MCQs Set 12

Answer: (a) non-corrosive

Explanation:
1. Surgical instruments must not react with body fluids.
2. Nb and Ta are highly resistant to corrosion, which is the property that makes them suitable.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) 21 to 30

Explanation:
1. The first series fills the 3d subshell, from scandium (Z = 21) to zinc (Z = 30).

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) Ag

Explanation:
1. Fe, V and Cu are 3d elements (Z = 26, 23, 29).
2. Ag (Z = 47) is a 4d element of the second series.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) It is paramagnetic

Explanation:
1. Fe is [Ar] 3d⁶ 4s²; \( \ce{Fe^{2+}} \) is [Ar] 3d⁶.
2. The 3d⁶ ion has four unpaired electrons, so it is paramagnetic. Ferromagnetism is a property of the bulk metal.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) their d-shells are complete

Explanation:
1. Zn (3d¹⁰ 4s²) and Hg (5d¹⁰ 6s²) have completely filled d subshells.
2. These filled d electrons do not take part in bonding, so only the two s electrons are lost.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) cuprous ion has a complete d-orbital and cupric ion has an incomplete d-orbital

Explanation:
1. \( \ce{Cu^+} \) is 3d¹⁰ and \( \ce{Cu^{2+}} \) is 3d⁹.
2. Colour needs a d-d transition, which requires a vacant place in the d subshell. Only the 3d⁹ ion has it.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) 3

Explanation:
1. Co is [Ar] 3d⁷ 4s².
2. Seven d electrons fill five orbitals as two paired orbitals and three singly occupied ones, so there are 3 unpaired electrons.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) IIB

Explanation:
1. Zn has the configuration 3d¹⁰ 4s², placing it in group 12, also called group IIB.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) \( \ce{Zn^{2+}} \)

Explanation:
1. \( \ce{Zn^{2+}} \) is 3d¹⁰, with all electrons paired.
2. \( \ce{Ni^{2+}} \) (3d⁸), \( \ce{Co^{2+}} \) (3d⁷) and \( \ce{Cu^{2+}} \) (3d⁹) all have unpaired electrons.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) Terbium

Explanation:
1. Cm, Cf and U are 5f elements.
2. Terbium (Z = 65) is a lanthanide.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) all of these

Explanation:
1. Small size and high charge give a high charge density, which attracts ligands strongly.
2. Vacant d orbitals accept the ligand lone pairs, so all three factors contribute.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) Bohr magneton

Explanation:
1. Magnetic moment is measured in Bohr magnetons (BM).

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) \( \ce{Ti^{4+}} \)

Explanation:
1. \( \ce{Ti^{4+}} \) has the configuration 3d⁰, so no d-d transition is possible.
2. The other three ions have 3d¹, 3d⁶ and 3d⁵ and are coloured.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) fourth period

Explanation:
1. The 3d series (Sc to Zn) lies in the fourth period.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) d⁵ s¹

Explanation:
1. The ground state of Cr is [Ar] 3d⁵ 4s¹, because half-filled d⁵ is extra stable.
2. So the outer arrangement is d⁵ s¹.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) of d⁵ configuration, metallic bonds are weak

Explanation:
1. Mn has the stable half-filled 3d⁵ configuration, so its d electrons are reluctant to take part in metallic bonding.
2. The weaker metallic bonding lowers its melting point compared with its neighbours.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) \( \ce{Cu^{2+}} \)

Explanation:
1. Unpaired electrons: \( \ce{Cu^{2+}} \) = 1, \( \ce{Ni^{2+}} \) = 2, \( \ce{Co^{3+}} \) = 4, \( \ce{Fe^{2+}} \) = 4.
2. The least magnetic moment belongs to the ion with the fewest unpaired electrons, \( \ce{Cu^{2+}} \).

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) 3d⁵ 4s²

Explanation:
1. The highest oxidation state equals the number of electrons in the (n-1)d and ns levels, if all are used.
2. 3d⁵ 4s² has seven such electrons, so it can reach +7 (Mn).

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) They crystallise with body-centred cubic and hexagonal close-packed structures only

Explanation:
1. Transition metals crystallise in bcc, hcp and also ccp (fcc) lattices, for example Cu, Ag and Au are fcc.
2. So the word 'only' makes that statement false.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) gold

Explanation:
1. Gold can be beaten into extremely thin leaf, making it the most malleable metal.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) containing unpaired electrons

Explanation:
1. Unpaired electrons have a net magnetic moment, so the substance is weakly attracted into a magnetic field.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (b) The ionic radii of trivalent lanthanides steadily increase with increase in atomic number

Explanation:
1. Because of lanthanide contraction, the ionic radii of \( \ce{Ln^{3+}} \) decrease steadily with atomic number.
2. The other statements are correct.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) all of these

Explanation:
1. All three have vacant d orbitals in their ions and form complexes such as \( \ce{[Ag(NH3)2]^+} \), \( \ce{[Au(CN)2]^-} \) and \( \ce{[Cu(NH3)4]^{2+}} \).

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (d) Both nickel and cobalt

Explanation:
1. Nickel is used in hydrogenation and cobalt in several industrial processes (for example hydroformylation).
2. So the answer is both Ni and Co.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (c) 3d⁵

Explanation:
1. Unpaired electrons are 1, 2, 5 and 3 respectively.
2. 3d⁵ has the most (5), and magnetic moment rises with the number of unpaired electrons.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.

Answer: (a) Cr

Explanation:
1. Cr is 3d⁵ 4s¹ with 6 unpaired electrons; Fe has 4, V has 3, Sc has 1.
2. Chromium has the maximum.

Teacher's Note:
1. Write the electronic configuration of the species first; most d-block questions follow from it.
2. Compare options using trends (oxidation states, size, magnetism) rather than memorising isolated facts.