Let us look at some of the topics covered in the revision notes of d and f block elements:

 

• Definition of d and f block elements

• Electronic Configuration

• Metallic character

• Ionic radii

• Melting point

• Oxidation state

• Catalytic property

• Complex formation

• Compounds of transitional elements

• Mercury Chlorides

 

1. The d-block elements are found in the centre of the periodic table and belong to groups 3 to 12.

2. The penultimate (last but one) shell is represented by (n – 1) in its overall electrical structure.

     3. Transition element: In its ground state or any of its oxidation states, the transition element is defined as one with                                incompletely filled d orbitals.

     4. Zinc, cadmium, and mercury are not considered transition metals due to completely filled d–orbital.

The elements that make up the f-block are those in which the 4 f and 5 f orbitals are gradually filled throughout the last two extended periods.

Lanthanide

Lanthanides are the 14 elements that follow lanthanum in the periodic table, from Cerium (58) to Lutetium (71). They are part of the first series of inner transitions. Lanthanum (57) possesses properties that are similar to those of lanthanum. As a result, it is investigated with lanthanide.

Actinoids

Actinides are the 14 elements with atomic numbers 90 (Thorium) through 103 (Lawrencium) that appear immediately after actinium (89). They are part of the second series of inner transitions. Actinium (89) displays similar qualities to that of actonoids. As a result, it is investigated with actinoids.

 

1. Transition series in 3D - The first transition series includes elements with atomic numbers ranging from 21(Sc) to 30(Zn) with incomplete 3d orbitals.

2. 4d – succession of transitions - Comprises elements with atomic numbers ranging from 39(Y) to 48(Cd) and incomplete 4d orbitals. It is known as the second transition series.

3. 5d – series of transitions - It consists of elements with incomplete 5d orbitals with atomic numbers 57(La), 72(Hf), and 80(Hg). It is known as the third transition series.

4. 6d – series of transitions - It is made up of elements with incomplete 6d orbitals with atomic numbers ranging from 89(Ac), 104(Rf), and 112(Uub). It is known as the fourth transition series.

 

a) Metallic nature: Transition elements are metallic in nature, meaning they have strong metallic connections due to the presence of unpaired electrons. This metallic nature results  in high density, high enthalpies of atomisation, and high melting and boiling temperatures.

b) Atomic radii: As the effective nuclear charge increases, the atomic radii drop from Sc to Cr. The pull caused by an increase in nuclear charge is cancelled by the repulsion caused by an increase in shielding effect; the atomic sizes of Fe, Co, and Ni are nearly identical. Since the shielding effect rises, and electron repulsions also increase.

 

c) Lanthanoid Contraction: As the atomic number grows, the atomic and ionic radii of transition metals decrease steadily. This is because the 4f orbitals are filled before the 5d orbitals. This size contraction, or lanthanoid contraction, is quite regular. The atomic radii of the second row of transition elements are practically identical to those of the third row of transition elements due to lanthanoid contraction.

d) Ionisation enthalpy: The ionisation energies of transition metals vary slightly and erratically due to atomic size variation. The ionisation enthalpy of the 5d transition series is higher than 3d and 4d transition series owing to lanthanoid contraction.

 

e) Oxidation state: Transition metals have varied oxidation states due to the tendency of (n-1)d and ns electrons to participate in bond formation.

f) Magnetic properties: Since most transition metals are ferromagnetic, they produce coloured compounds. This occurs primarily due to the existence of unpaired electrons. It rises from Sc to Cr and then drops due to an increase in the number of unpaired electrons, which rises from Sc to Cr and then drops. They are rarely ferromagnetic.

 

g) Catalytic properties: Most transition metals, such as Fe, Ni, V2O3, Pt, Mo, and Co, are used as catalysts due to (i) the existence of incomplete or empty d – orbitals, (ii) large surface area, (iii) variable oxidation state, and (iv) capacity to form complexes.

h) Colored compound formation: Due to the existence of incompletely filled d – orbitals and unpaired electrons, they create coloured ions that can undergo a d – d transition by absorbing visible colour and radiating complementary colour.

 

i) Complex formation: Transition metals form complexes due to (i) the presence of sufficient energy unoccupied d – orbitals, (ii) smaller size, and (iii) increased charge on cations.

j) Interstitial compounds: Transition metals feature spaces or interstitials in which C, H, N, B, and other elements can fit, resulting in the production of interstitial compounds. They are non-stoichiometric, which means their composition is not constant, such as steel. They are denser, less malleable, and less ductile.

 

k) Alloy formation: They form alloys because their ionic sizes are similar. Metals, such as brass, bronze and steel, can be substituted in a crystal lattice.

• It is a well-known alloy that consists of a lanthanoid metal and iron and traces of S, C, Ca and Al.

• A good deal of mischmetal is used in Mg-based alloy to produce bullets, shells and lighter flint.

 

The properties of d-block elements are listed below.

1. These have a metallic appearance.

2. They are durable and possess a high density.

3. Their melting and boiling points are quite high.

4. They display a range of oxidation states.

5. They produce a variety of coloured ions and compounds.

6. The atomic radii decrease as the atomic number increases.

 

The general properties of f-Block elements are listed below.

1. They are paramagnetic in nature, with a higher proportion of radioactive elements than the other blocks.

2. They exhibit a range of oxidation states.

3. They have a shielding effect on them. Shielding occurs when an electron's attraction to an atom decreases as it moves away from the nucleus. This is due to the weakening of the forces that hold atoms together as distance rises.

 

1. Write down the electronic configuration of:

(i) Cr³⁺ (ii) Pm³⁺ (iii) Cu⁺ (iv) Ce⁴⁺ (v) Co²⁺ (vi) Lu²⁺ (vii) Mn²⁺  (viii) Th⁴⁺

Ans :

(i) Cr³⁺: 1s2 2s2 2p6 3s2 3p6 3d3

Or, [Ar]18 3d3

(ii) Pm³⁺: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f4

Or, [Xe]54 4f4

(iii) Cu⁺: 1s2 2s2 2p6 3s2 3p6 3d10

Or, [Ar]18 3d10

(iv) Ce⁴⁺: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6

Or, [Xe]54

(v) Co²⁺: 1s2 2s2 2p6 3s2 3p6 3d7

Or, [Ar]18 3d7

(vi) Lu2+: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d1

 Or, [Xe]54 4f14 5d1

(vii) Mn²⁺: 1s2 2s2 2p6 3s2 3p6 3d5

Or, [Ar]18 3d5

(viii) Th⁴⁺: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6

Or, [Rn]86

      2. Why are Mn2+ compounds more stable than Fe towards oxidation to their +3 state?

Ans : Electronic configuration:               Fe²⁺ is [Ar]18 3d6.

Mn²⁺ is [Ar]18 3d5.

We know that half and completely filled orbitals are more stable. Hence, Mn with (+2) state has a stable d5 configuration, which is why Mn²⁺ shows resistance to oxidation to Mn³⁺. We know that, Fe²⁺ has 3d6 configuration, and by losing one electron, its configuration changes to a more stable 3d5 configuration. Therefore, Fe²⁺ easily gets oxidised to Fe⁺³ oxidation state.

Learn more about the subject and related topics with MSVGo. MSVGo is an online learning app that can make understanding maths and science concepts easy. With 15,000+ videos, 10,000+ questions bank, and video solutions to textbook questions, the MSVGo can become your study buddy. Get the app for free and become an MSVGo Champ today! https://msvgo.com/