NCERT Class 12 Chemistry Chapter 8 Notes The d and f-Block Elements - Download PDF

CBSE Class 12 Chemistry chapter 8 notes provides a brief synopsis of the chapter The d and f block elements. The Class 12 Chemistry chapter 8 notes are helpful for students who want to understand the periodic table in a simple manner. The periodic table is merely one aspect of chemistry, while it has the potential to intimidate kids. The notes for Class 12 Chemistry chapter 8 chapter will undoubtedly change that.

As a result, students can study it in groups. So, the table's d-block and f-block elements will be the only ones discussed in this chapter. As a result, the plus two chemistry d and f block elements notes will help you study more efficiently. These short notes are based on the most recent CBSE Syllabus for CBSE Class 12 Chemistry and are beneficial for CBSE Class 12 board examinations. The main topics covered in The d and f block elements class 12 notes are the physical properties of d block elements, some important compounds of transition metals, lanthanoids, actinoids, lanthanide contraction etc. For a more detailed explanation of these concepts, see The d and f Block Elements notes class 12. The CBSE class 12 chemistry ch 8 notes can help students understand more about these subjects.

Also, students can refer,

• NCERT Notes Class 12 Chemistry
• NCERT Solutions for class 12 Chemistry Chapter 8 The d and f block elements
• NCERT Exemplar Class 12 Chemistry Chapter 8 Solutions The d and f block elements

NCERT Class 12 Chemistry Chapter 8 Notes

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 1

d-block Elements

The d block of the periodic table is made up of elements from groups 3 - 12.The d orbital of the d-block elements is filled in four periods. The transition metals are divided into three series: 3d from Sc to Zn, 4d from Y to Cd, and 5d from La to Hg. The fourth 6dseries begins with Ac and is currently unfinished.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 2

Position of d block in the Periodic Table

In the periodic table, the d-block elements are found in the intermediate region of the s- and p-block elements. Because of its location between s- and p-block components, it was given the term 'transition.'

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 3

Electronic Configuration of d Block Elements

(n-1) d^1-10ns^1-2 is the electronic configuration of d-block elements. They have two outer shells that aren't complete.

Where (n–1) denotes inner d orbitals with electrons ranging from 1 to 10, and ns denotes the outermost orbital, which may have one or two electrons (n-1) The electronic configurations of Zn, Cd, and Hg are represented by d¹⁰s².

d block elements have a variable valency that varies by one unit.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 4

Physical Properties

In CBSE Class 12 Chemistry chapter 8 notes, Physical Properties are Discussed as follows:

• Metallic characteristics

All transition metals have metallic character. They are excellent heat and electricity conductors. They are abrasive and persistent. They are malleable, ductile, and resonant since they are metal. They combine with other metals to form alloys. They can be found in three different structures: face-centered cubic (fcc), hexagonal close-packed (hcp), and body-centered cubic (bcc).Within the atoms of transition elements, there is both covalent and metallic bonding.

• Atomic size

As the atomic number increases, the atomic radii of the elements in the 3d-series decrease. Because of lanthanoid contraction, the atomic radii rise from 3d to 4d, and the atomic radii of the 4d and 5d transition series are quite close. Zirconium and Hafnium, are example. The rise in the density of elements is caused by a decrease in the metallic radius due to an increase in the atomic mass. As a result, the density of titanium to copper increases.

• Ionisation enthalpy

Because transition elements are tiny, they have a high ionisation energy.Since their ionisation potentials lie between S and P block elements, they are less electro positive than s-block elements. Transition elements form covalent compounds. The ionisation potentials of the d-block elements increase from left to right due to the screening effect of the additional electrons added to the (n-1) d subshell. Because of the stable electronic configuration, the second ionisation energy increase with the increase in atomic number in the first transition series. Ionization energy reduces as move through the group whereas the amount of ionisation energy increases across the period.

• Oxidation state

The small energy difference between the ns and (n -1) d orbitals cause transition elements to have different oxidation states. (n -1) d electrons participate in bonding with ns electrons. Scandium, on the other hand, does not have different oxidation states due to the limited number of electrons available for bonding. Zinc has fewer orbitals accessible for bonding due to the existence of more d electrons, and so does not have a variable oxidation state. The elements in the 8th group have the highest oxidation state among the d-block elements. Manganese, which belongs to the 7th group, has the highest oxidation state among the 3d –series elements. Ruthenium, which belongs to the 8th group, has the highest oxidation state among the 4d-Series elements. Osmium, which belongs to the 8th group, has the highest oxidation state of all the elements in the 5d-Series.

• Magnetic properties

Transition metals and most of their compounds are paramagnetic in nature. The spin only formula is used to compute the magnetic moment of these elements.

μ =n(n-1)

where n is the number of unpaired electrons

• Formation of coloured compounds

There is an excitation of electron from lower to higher level and the energy of excitation corresponds to the energy difference between the levels.This frequency is usually in the visible range. The existence of unpaired or incomplete d-orbitals gives the transition metal ions their colour. The transition metal cations' absorption of visible light and hence their colourful character is due to the transition of one or more unpaired d-electrons from a lower to a higher level within the same d-subshell. This transition requires a small amount of visible light energy.Sc³⁺, Cu⁺,Zn²⁺, and Ti⁴⁺ have either a completely empty or completely filled 3d-orbital, i.e. no unpaired d-electron, and hence appear colourless.

• Formation of complex compounds

Transition metal cations have a strong tendency for forming complexes with several molecules or ions known as ligands. Such complexes are named coordinate complexes because the links involved in their formation are coordinate. The structure of these complex ions might be linear, square, planar, tetrahedral, or octahedral, depending on the nature of the metal ion hybridization. Weak ligands like CO and NO form complexes only when transition metals are in zero oxidation state.This is because these ligands contains empty orbitals in the donor atom in addition to the lone pair of electrons. Highly electronegative and basic ligands like F^-, Cl^- can form complexes with transition metals despite being in high oxidation states due to the presence of small, highly charged or neutral ligands with lone pair of electrons that can form strong sigma bonds by donating a lone pair of electrons.The stability of complexes increases as the atomic number increases in a transition series. The transition metal atom has several oxidation states; the higher the valence, the more stable the complex.

• Formation of interstitial compounds

Interstitial compounds with non-stoichiometric composition are formed when transition elements combine with tiny atoms such as H, B, C, N, and others. The resulting interstitial compounds are chemically inert and have higher melting points than pure metals. These compounds are strong and durable, and they maintain metallic conductivity.

eg : TiH_1.3,VH_0.54

• Alloy formation

Alloys are homogenous mixes of more than one metal. Transition metals are generally smaller in size. So they can displace another metal from the crystal lattices and there by forming alloys. Alloys are hard and have high melting points. Ferrous alloys include chromium, vanadium, tungsten, manganese, and molybdenum, for example. Brass (alloy of copper + zinc), stainless steel, bronze (alloy of copper + tin), and so on are some additional examples.

• Formation of non-stochiometric compounds

Non-stoichiometric compounds are those in which the chemical composition does not match the ideal chemical formula. Variable valency in transition metals, as well as defects developing in the solid state, cause these compounds to form. Such compounds include those made using O, S, Se, Te, Fe, Zn, and many other elements.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 5

Some Important Compounds of Transition Metals

According to the d and f block elements Class 12 notes, some of the important compounds are:

1. Potassium dichromate (K₂Cr₂O₇)

Preparation

Initially, chromite ore was fused with sodium or potassium carbonate in the presence of air.

A sodium chromate solution is filtered and then acidified with a sulfuric acid solution, yielding an orange sodium dichromate solution that can be crystallized.

Because sodium dichromate is more soluble than potassium dichromate, it is fused with KCl, resulting in the formation of orange potassium dichromate crystals.

The dichromates and chromates exist in equilibrium at pH 4 and can be interconverted.

In the presence of an acidic medium, the yellow colour of chromate changes to an orange-colored dichromate, whereas in the presence of a basic medium, the dichromate transforms back to chromate.

Properties

• In an acidic media, potassium dichromate is a powerful oxidizing agent.

• Heat causes potassium dichromate to decompose, resulting in the formation of potassium chromate, chromic oxide, and oxygen

2. Potassium permanganate (KMnO₄)

• Potassium Permanganate is a dark purple solid made up of two ions: potassium and permanganate. Because it is a strong oxidizing agent with medicinal qualities, it is frequently used to clean wounds and treat dermatitis.

• In the presence of air or an oxidizing agent, fusion of powdered Pyrolusite ore with an alkali metal hydroxide like KOH results in the formation of dark green potassium Manganate, which disproportionates in a neutral or acidic solution and results in the formation of potassium permanganate.

• Commercially, potassium permanganate is made by alkaline oxidative fusion of Pyrolusite ore followed by electrolytic oxidation of manganate (4) ion.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 6

f-block Elements

f-block elements are those that have gradually filled f orbitals.The elements of the inner transition metals' 4f series are known as lanthanoids, while the elements of the 5f series are known as actinoids.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 7

Lanthanoid

Lanthanoid has an electronic configuration of [Xe] 4 fn⁺¹ 5 d¹ 6 s² or [Xe] 4 fn⁵ d¹ 6 s², with a valence shell electronic configuration of 4 f^1-146s²

They have oxidation states of +3, +2, and +4

The first members of this series are mildly reactive to calcium, and their behaviour gradually resembles that of aluminium as the atomic number increases.

Lanthanides mix with hydrogen when exposed to mild heat.

Carbides and halides are formed when they are heated with carbon (in presence of halogens while burning).

Lanthanides react with dilute acids to produce hydrogen gas.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 8

Lanthanide Contraction

As we move through the lanthanoid series, the atomic number, or the number of electrons and protons, gradually increases by one. The effective nuclear charge increases as electrons are added to the same shell. As the atomic number rises, so does the amount of electrons in the 4f orbital, which has a weak shielding effect and increases the effective nuclear charge on the outside electrons. As a result, the size of lanthanoids reduces with increasing atomic number, a phenomenon known as lanthanoid contraction. The features of the second and third transition series are comparable as a result of lanthanoid contraction.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 9

Actinoids

The elements Th to Lr are members of the Actinoids series, which consists of 14 elements. They are radioactive substances. The former elements have extended half-lives, whereas the subsequent elements, such as lawrencium with atomic number 103, have half-lives ranging from one day to three minutes. The electronic configuration of actinoids is 7s², with inconstant occupancy of the 5f and 6d subshells. Because of the poor screening effect of nuclear charge exerted by the f electrons, the ionic radii gradually decrease across the series. Actinoid contraction is the term for this.

In this way, Class 12 The d and f block elements notes explain the term actinoids.

NCERT Class 12 Chemistry Chapter 8 Notes: Topic 10

Comparison Between Lanthanoid and Actinoid

NCERT notes for Class 12 Chemistry chapter 8 gives the comparison between lanthanoid and actinoid as:

• Atomic and ionic sizes

Actinoids' ionic radii gradually decrease across the series, similar to lanthanoids, due to the poor screening effect of nuclear charge exerted by the f electrons.

• Oxidation states

The lanthanide have oxidation states of +3. Due to the additional stability of fully-filled and half-filled orbitals, some elements may show + 2 and + 4 oxidation states.

Actinoids, on the other hand, have a + 3 oxidation state. Due to the similar energies of 5f, 6d, and 7s, they also have different oxidation states.

• Chemical reactivity

The lanthanide series' earlier members are more reactive. With rising atomic number, they resemble Al. Finely split actinoids are highly reactive metals that produce a mixture of oxide and hydride when introduced to boiling water. Actinoids mix with the majority of non-metallic elements at moderate temperatures. The action of alkalies has little effect on actinides, while nitric acid has a minor effect due to the creation of a protective oxide layer.

These topics are included in Class 12 Chemistry chapter 8 notes pdf download and the d and f block elements Class 12 pdf download.

Significance of NCERT Class 12 Chemistry Chapter 8 Notes

A good comprehension of ideas is required to attempt and answer problems in the chapter d and f block elements. The d and f Block Elements notes class 12 have been structured to make it easier for students to study and comprehend the material. CBSE class 12 chemistry ch 8 notes are helpful in covering the major themes in the CBSE Chemistry Syllabus for Class 12. This note is also very helpful for the preparation of competitive exams like NEET, JEE MAIN etc. Students can use the Class 12 Chemistry chapter 8 notes pdf download to study offline. Chemistry class 12 chapter 8 notes pdf helps students to revise the topics at any time.

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