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NCERT Solutions for Class 12 Chemistry Chapter 4 – The D and F Block Elements
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Intext Questions with Solutions of Class 12 Chemistry Chapter 4 – The D and F Block Elements
4.1

📌 Key Points to Note from Question
Given Data:
- Silver has a completely filled 4d10 orbital in its ground state.
Key Concept:
- A transition element is defined as an element that has an incomplete d-subshell in either its atomic state or any of its common oxidation states.
Ans – Ag (Z=47) has an external electronic structure of 4d105s1. In AgO & AgF2, it displays +1 & +2 O.S. Additionally, the electrical arrangement in +2 O.S. is d9, meaning that the d-subshell is not full. As a result, it serves as a shift component.
4.2

📌 Key Points to Note from Question
Given Data:
- Series: Sc (Z = 21) to Zn (Z = 30)
- Enthalpy of atomization of Zn = 126 kJ mol-1 (lowest in the series)
Key Concept:
- Enthalpy of atomization depends on the strength of metallic bonding.
- Metallic bonding strength is influenced by the number of unpaired d-electrons.
What to Find:
- Why zinc has the lowest enthalpy of atomization in the 3d series.
Ans – The durability of the crystal lattice and the resilience of the bond between metals are closely related to the enthalpy of atomization. Because the orbital components are occupied in the instance of zinc (3d104s2), none of the electrons from the 3d-orbitals play a role in the creation of metallic bonds. Nevertheless, a few d-electrons contribute to the metallic bonds in each additional component in the 3d group. This indicates that zinc has the smallest enthalpy of atomization in the 3d family and more fragile metallic bonds.
4.3

Ans – Manganese has the highest number of O.S. (Z = 25). Its external EC is 3d54s2, which explains this. It has the most e-1 s to shed or exchange since 3d and 4s have similar energies. As a result, it displays O.S. between +2 and +7, which is the highest value.
4.4

📌 Key Points to Note from Question
Given Data:
- Eo(M2+/M) for copper = +0.34 V
What to Calculate:
- Why the standard reduction potential of copper is positive.
Ans – Each metal’s Eo(M2+/M) is correlated with the total of the enthalpy shifts that occur in the subsequent stages:

Cu possesses a minimal enthalpy of hydration (ΔhydH) and an elevated enthalpy of atomization (ΔaH). The hydration enthalpy of Cu(s) is insufficient to offset the considerable energy needed to convert it to Cu2+(aq). Eo(Cu2+/Cu) is consequently affirmative.
4.5

📌 Key Points to Note from Question
Key Concept:
- Stable Electronic Configurations: Half-filled and fully filled d-orbitals lead to higher ionization enthalpies (e.g., Cr and Cu).
- Increasing Nuclear Charge: Ionization enthalpy generally increases across the period but is affected by electron repulsions and subshell stability.
- Exchange Energy: Elements with stable configurations (like Mn, Cr, and Cu) show deviations due to extra stability from exchange energy.
Ans – Whenever an e-1 is eliminated, the energy levels of the 4s and 3d orbitals alternate, causing a shift in the IEs of the 3d series. Ionization is therefore accompanied by a reorganization activity. In the dn arrangement, this leads to the discharge of exchange energy, which rises as the total amount of e-1 s grows. Since the loss of 1 e- provides steady EC (3d6), Cr has a modest first IE. Since e~ must be eliminated from the steady configuration’s 4s orbital (3d10 4s2), zinc has an exceptionally great IE. It gets challenging to remove the second e- after losing the first. Second IEs are therefore greater and often rise from left to right since the stable arrangement of Cr+ (3d5) & Cu+ (3d10) requires the removal of the second e–, Cr, and Cu exhibit substantially larger ratios.
4.6

Ans – The electronegativity ratings of oxygen & fluorine are fairly significant. The metallic substances can be oxidized to their maximum oxidation state by them. Consequently, the fluorides and oxides derived from metallic substances, especially transition alloys, exhibit the greatest oxidation states.
4.7

Ans – Compared to Fe2+, Cr2+ is a more potent reducing agent. In contrast to E°(Fe3+/Fe2+), which is positive (+ 0.77 V), E°(Cr3+/Cr2+) is negative (- 0.41 V). Therefore, whereas Fe2+ cannot readily oxidize to Fe3+, Cr2+ may readily oxidize to Fe3+.
4.8

Ans – Electronic configuration of M (Z = 27) is [Ar] 3d74s2
⇒ Electronic configuration of M2+(aq) is [Ar] 3d74s0

4.9

📌 Key Points to Note from Question
Key Concept:
- High Hydration Enthalpy of Cu2+
- Low Stability of Cu+ in Water
Ans – Whereas Cu2+ (aq) remains steady, Cu+ (aq) is unstable. This happens because Cu2+(aq) has a substantially greater ΔhydH compared to Cu+(aq), which makes up for the second IE of Cu. Certain Cu(I) groups are therefore volatile in aqueous solution and have experienced the following uneven distribution: 2 Cu+ —–> Cu2+ + Cu.
4.10

📌 Key Points to Note from Question
Key Concept:
- Actinoids have a greater nuclear charge (Z) and higher 5f electron involvement.
- In actinoids, 5f electrons are less shielded, leading to stronger attraction and greater contraction.
Ans – Since 5/ electron particles have a worse shielding impact than 4f electrons, actinoid contraction—the reduction or contraction of atomic and ionic radii in actinoid elements—is greater than lanthanoid shrinkage. As a result, actinoid atoms are more susceptible to the physical contraction caused by a rise in the charge of their nuclei.
Exercise Questions with Solutions of Class 12 Chemistry Chapter 4 – The D and F Block Elements
4.1

Ans –

4.2

📌 Key Points to Note from Question
Key Concept:
- Mn2+ has a stable half-filled d-orbital configuration (3d5).
- Fe2+ has a less stable d⁶ configuration, which is prone to oxidation to Fe3+.
Ans – Mn2+ has an electronic structure of 3d5. This setup is reliable since it is partially filled. As a result, the third ionization enthalpy is extremely high, meaning that the 3rd electron is difficult to lose. Fe2+ has the electronic structure 3d6. It may readily lose a single electron to reach an intact 3d5 structure.
4.3

📌 Key Points to Note from Question
Key Concept:
- In the +2 oxidation state, the transition metal loses two electrons, leading to a more stable configuration.
- The stability of the +2 state increases due to the gradual filling of the 3d orbitals, resulting in a more stable electronic configuration.
Ans – In this section, the j-orbitals lose two electrons, and as the number of atomic particles rises, the 3d-orbital eventually becomes saturated. The long-term reliability of the cations (M2+) rises from Sc2+ to Mn2+ as the amount of electrons with no pairings in the 3d orbital gets higher.
4.4

📌 Key Points to Note from Question
Key Concept:
- Stability of oxidation states is influenced by the electronic configuration.
- The stability is highest when the resulting electronic configuration is either fully filled or half-filled (due to stability from symmetry and exchange energy).
Ans – The oxidation states that result in precisely partially packed or entirely occupied d-orbitals are more durable in the initial set of transition materials. For instance, the electronic structure of Mn (Z = 25) is [Ar] 3d5 4s2. Mn (II) exhibits oxidation states ranging from + 2 to + 7. However, its partially filled structure [Ar] 3d5 makes it the most robust. Because its f-orbitals are partially occupied Sc3+ is less volatile than Sc+, while Fe3+ is a lot more durable than Fe2+.
4.5

📌 Key Points to Note from Question
Key Concept:
- Stability of oxidation states is influenced by the electron configuration, particularly favoring half-filled or fully filled d-orbitals.
- 3d5 configuration is particularly stable (half-filled d-orbital).
- 3d10 is also stable (fully filled d-orbital).
Ans –

4.6

📌 Key Points to Note from Question
Key Concept:
- The oxometal anions where the metal exhibits an oxidation state equal to its group number are formed when the metal is in its highest oxidation state.
Ans –

4.7

📌 Key Points to Note from Question
Given Data:
- Lanthanoids are the 14 elements with atomic numbers from 58 (Cerium, Ce) to 71 (Lutetium, Lu).
Key Concept:
- Lanthanoid Contraction: The progressive decrease in the ionic and atomic radii of the lanthanoid elements due to poor shielding of the nuclear charge by the 4f electrons.
- Cause: The 4f electrons in lanthanoids do not shield the nucleus effectively, leading to increased effective nuclear charge, which pulls the electrons closer to the nucleus, resulting in a contraction of size.
Ans – Lanthanoid Contraction: The electrons that reside in the 4f-subshell of lanthanoids are filling up. The nuclear energy grows as one moves from left to right, and this rise should be offset by the four f-electron filtering impact expanding in strength. Nevertheless, the protective impact of the f-electrons is quite weak. Lanthanoid contraction is the result of the atomic & ionic radii decreasing from left to right.
Here are the Lanthanoid Contraction’s effects,
(a) Isolation Lanthanoids: It is challenging to distinguish among lanthanoids because of their comparable characteristics.
(b) Change in the basic strength of hydroxides: Lanthanoid contraction causes M3+ ion size to dip, which in turn causes the covalent nature of the M—OH bonding to rise. Hence, Lu(OH)3 replaces La(OH)3 as the basic character of oxides and hydroxides.
(c) The atomic dimensions of the substances belonging to the same class from the second and third transition periods are identical. The discrepancy between the values of Zr and Hf is much smaller than the distinction between the atomic radii of Y and La. The lanthanoid contraction is the reason behind this.
(d) Change in conventional reduction possibility: Because of lanthanoid contraction, the average reduction potential (E°) for the reduction operation increases slightly but steadily.
M3+ (aq) + 3e– —–> 4 M(aq)
(e) Changes in physical characteristics, such as hardness, boiling & melting points.
4.8

Ans – Transitional components’ basic attributes.
(i) Electronic setup – (n -1) d1-10 ns1-2
(ii) Metallic traits: They generally exhibit conventional metallic shapes, with the notable neglect of Zn, Cd, and Hg.
(iii) Ionic and atomic dimensions: Ions with the same energy in a sequence exhibit a gradual reduction in diameter as the atomic number rises.
Oxidation condition: Variable, with a range of +2 to +7.
(v) Paramagnetism: Ions including electrons with no pairs exhibit paramagnetic behavior.
(vi) As the charge gets bigger, so does the ionization enthalpy.
The presence of electrons without pairings causes colored ions to form.
(viii) Complex compositions are formed as a result of the metal ions’ tiny dimensions and high energy saturation.
(ix) Because they can transform into various levels of oxidation, they have catalj¯c characteristics.
(x) Interstitial chemical creation.
(xi) Synthesis of alloys. They fall into the category of s & p-block components and are referred to as transitional substances because of their partially filled d-orbitals in the state of equilibrium or any acceptable oxidation condition. Since their ground states contain completely occupied d-orbitals, Zn, Cd, and Hg could not be considered transitional components.
4.9

Ans – Electronic equation of transition substances: (n – 1)d1-10 ns1-2. Non-transition components’ electronic arrangement: ns1-2 or ns2np1-6. Comparatively speaking, it is clear that non-transition ions lack d-orbitals in their atoms’ valence shells, whereas transitional substances have partial d-orbitals (or s-orbitals in certain situations). This explains why the components that correspond to various groups of structures have different features.
4.10

Ans – Lanthanides display oxidation states of +2, +3, and +4. The predominant oxidation state of lanthanoids is +3.
4.11

Ans – (i) Magnetic characteristics: Transitional substances and many of their analogs are paramagnetic, meaning that a magnetic field only faintly attracts them. This is because atoms, ions, or molecules contain electrons with no pairing as the number of electrons without pairings rises, the paramagnetic property will also get increased. The area of magnetic attraction is used to quantify the paramagnetic nature, and the result will be as follows,

(ii) They are capable of greater interatomic interactions which leads to deeper metallic bonds between atoms due to the huge amount of electrons without pairings in their d-orbitals, which raises the degree of atomization.
(iii) An extremely frequent property of transition alloys is the development of colored substances, both in solidified form and in aqueous solution. This is because some ultraviolet radiation is absorbed, which causes the electrons in conversion metal atoms to undergo a d-d transition. Electrons can move from a single collection of d-orbitals to another group inside the identical sub-shell. The d-orbitals lack an identical amount of energy and can divide into two distinct groups of orbitals that have various energies when ligands are present. We refer to these transitions as d-d transitions. For those d-d adjustments, the energy disparity is in the optical range. When elements made from transition metals are exposed to white light, they collect a certain frequency and release the extra colors, giving the complicated substance its distinctive color. Since they don’t absorb any light in the evident spectrum, Zn2+ and Ti4+ salts appear white.
(iv) Catalytic assets: Many transition metals and their mixtures function as catalysts in a range of processes. For example, Haber’s process uses finely split iron to produce NH3, while the Contact method uses Pt or V2O5 to produce H2S04. The subsequent 2 variables are responsible for the catalytic process.
(a) A novel pathway to a reaction with less activation energy is made possible by the transition metal ion’s capacity to move “easily” between oxidation states.
(b) The transition metal’s surface functions as an excellent adsorption increasing the percentage of reacting substances on it and triggering the chemical process.
4.12

Ans – There are several interstitial molecules that transition metals may create. Microscopic atoms from substances such as H, G, N, B, and so on can be trapped in their crystal lattice and may even form weak connections with them. They become less malleable and ductile and more compressive due to the production of interstitial complexes. Compared to wrought iron, steel, and cast iron are harder because of confined carbon atoms in the interstitial gaps.
4.13

Ans – Owing to the involvement of (n – 1) d electrons alongside the ns electrons in the bond growth, transition alloys exhibit a variety of different states of oxidization. As a result, they show a wide range of different oxidation levels. However, the non-transition metals that are often found in the s-block do not exhibit varied oxidation states because they obtain the arrangement of the closest precious gas components through the elimination of valence s-electrons.
The inert pair impact in the p-block favors the more powerful constituents in the simpler oxidation states, but in the d-block, the converse is true. Mo(VI) and W(VI), for instance, have been demonstrated to be more resistant to corrosion than Cr(VI) in category 6. Therefore, while MoO3 & WO3 are weak oxidizers, Cr(VI) is in its current state of dichromate in an acidic media.
4.14

Ans – Chromite ore (FeCr2O3) is fused with sodium carbonate in an unrestrained surplus of air to produce chromate, which is then used to make potassium dichromate. The following is the outcome of what happens with sodium carbonate:
4FeCr2O4 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2
Orange sodium dichromate (Na2Cr,07.2H20) can be crystallized from the yellow sodium chromate mixture after it has been filtered & acidified with sulfuric acid.
2Na2CrO4 + 2H+ → Na2Cr2O7 + 2Na+ + H2O
Compared to potassium dichromate, sodium dichromate remains highly soluble. Consequently, the final product is made by adding potassium chloride to the sodium dichromate approach.
Na2Cr2O7+ 2KCl → K2Cr2O7 + 2NaCl
Potassium dichromate crystallizes as orange flakes. The pH of the fluid affects the chromates & dichromates. Potassium dichromate turns into yellow potassium chromate when its pH is raised.
2CrO42- + 2H+ → Cr2O72- + H2O
Cr2O72- + 2OH– → 2CrO42- + H2O
4.15

Ans – K2Cr2O7 is a powerful oxidising agent. In a dilute sulphuric acid solution, the oxidation state of chromium transitions from +6 to +3.

4.16

Ans – Pyrolusite (MnO2), potassium hydroxide & O2 are combined to create potassium permanganate (KMn04); initially, green potassium manganate is produced. 2K2MnO4 + 2H20 —> 2MnO2 + 4KOH + O2 Water is used for separating potassium manganate, which is subsequently disproportionated in an acidic or neutral solution to produce potassium permanganate.




4.17

Ans – (i) The reduction potential of Cr3+/Cr2+ is negative. Therefore, it is not possible to convert Cr3+ to Cr2+. The positive redox capacity of Mn3+/Mn2+ is high. Therefore, it is easy to decrease Mn3+ to Mn2+. The positive reduction capacity of Fe3+/Fe2+ is limited. Fe3+ is more volatile than Cr3+ but highly durable than Mn3+.
(ii) Based on the E° standards, the metal oxidizes to the divalent cation in the following sequence: Mn > Cr > Fe.
4.18

📌 Key Points to Note from Question
Key Concept:
- Transition metal ions exhibit color in aqueous solutions because they have partially filled d-orbitals, which allow absorption of specific wavelengths of light.
- The color depends on the d-d transitions, where electrons move between different energy levels within the d-orbitals.
Ans – Particularly ions with empty d-orbitals will be colored. Colorless ions have either full or vacant d-orbitals. In light of this, the colored ions in the above table are:
Ti3+(3d1), V3+(3d2), Mn2+(3d5), Fe3+(3d5), Co2+ (3d7)
Sc3+ (3d°) and Cu+ (3d10) ions remain colorless in nature.
4.19

Ans – Because the total of the initial and secondary ionization energy increases, the degree of stability of the +2 oxidation stage in the initial transition sequence often falls from left to right. Nevertheless, partially filled d-orbitals (3d5) make Mn2+ more durable, whereas filled d-orbitals (3d10) make Zn2+ have greater stability.
4.20

Ans – (i) Electronic structure: Lanthanoids’ typical electronic setup can be depicted as [Xe]54 4f1-14 5d0-1 6s2 compared to actinoids is [Rn]86 5f0-14 6d0-1 7s2. Actinoids are members of the 5f series, while lanthanoids are members of the 4f series.
(ii) Atomic & ionic dimensions: When we move from left to right in the +3 oxidation state, each of the atoms or ions within both actinoids & lanthanoids exhibit a drop in size. The reduction is known as lanthanoid constriction in lanthanoids and actinoid relaxation in actinoids. Because 5f electrons provide less protection, the contractility increases from element to element in actinides.
(iii) Oxidation condition: Actinoids exhibit +3, +4, +5, +6, and +7 oxidation stages, while lanthanoids exhibit a restricted number of oxidation types (+2, +3, +4), with +3 being the most prevalent. The significant energy difference that exists among the 4f, 5d, and 6s orbitals is the source of this. Nevertheless, due to the tiny energy gap between the 5f 6d and Is orbitals, actinoids exhibit a vast range of different levels of oxidation.
(iv) Reactivity of chemicals: The early lanthanoids perform progressively more like aluminium as their atomic no. Increases, yet they’re still highly reactive like calcium. Whenever metallic substances are gradually warmed in the gas, they mix with the H2 as well. Warming the metals with carbon results in the formation of carbides, Ln3C, Ln2C3, and LnC2. They ignite in halogens to generate halides and release hydrogen from diluted acid. They produce the hydroxides M(OH)3 & oxides M2O3.
Particularly whenever precisely split, actinoids are very reactive metals. They react with water that is boiling to form an equilibrium of hydride and oxide, and at relatively low temperatures, they combine with the majority of non-metals.
Each of the metals is attacked by HCl, although most are only marginally impacted by nitric acid because defensive oxide coatings develop; alkalis are ineffective. Because actinoids have larger atoms and smaller ionization energies than lanthanoids, they become increasingly reactive.
4.21

📌 Key Points to Note from Question
Key Concept:
- Transition Metal Chemistry: Stability of oxidation states depends on electron configuration and the relative stability of half-filled or fully filled d-orbitals.
- Reducing vs Oxidizing Behavior: Ions with d⁴ configurations can easily lose or gain electrons depending on their relative stability.
Ans – (i) While the E° measurement for Mn3+/Mn2+ is favorable (+1.57 V), the E° value for Cr3+/Cr2+ is adverse (-0-41 V). Thus, Mn3+ may readily experience a reduction to yield Mn2+ and so operate as an oxidizing substance, while Cr2+ ions can readily encounter oxidation to provide Cr3+ ions by serving to become powerful reducing agents.
(ii) Compared to Co (II), Co (III) is more likely to form coordinating groups. Therefore, Co (II) transforms into Co (III) to be readily oxidized with the inclusion of ligands.
(iii) To obtain a stable d° structure, ions having a dx arrangement are prone to lose the lone electron in the d-subshell. As a result, they become fragile and oxidize or disproportionate.
4.22

Ans – When a material experiences both oxidation and reduction or when a component’s no. of oxidation processes rises and falls to produce 2 distinct goods, this is known as a disproportionation event.

4.23

📌 Key Points to Note from Question
Key Concept:
- Stability of +1 Oxidation State: Depends on the ionization energy and electronic configuration.
- Cu+ Stability: Influenced by high ionization energy and low hydration energy.
Ans – Since the cation or positive ion gains an upright state structure of d-orbitals (3d10) by shedding 1 electron, Cu with arrangement [Ar] 4s13d10 displays a +1 oxidation condition and produces the Cu+ ion.
4.24

📌 Key Points to Note from Question
Key Concept:
- Electronic Configuration Rule: Remove electrons from 4s before 3d when forming cations.
- Stability in Aqueous Solution: Depends on high hydration energy and stable half-filled or fully-filled d-orbitals.
Ans – Mn3+ = 3d1 = 4 electrons without any pairs, Cr3+ = 3d3 = 3 electrons pairs, V3+ = 3d2 = 2 set of electrons, Ti3+=3d1 = l electron. From the above electron ranges, Cr3+ remains highly stable in an aqueous solution due to the half-filled t2g stage.
4.25

Ans – (i) Owing to every atom of metal possessing a reduced oxidation range, the less reactive oxide of a transition metal is neutral, while the more reactive oxides are acidic by virtue of their elevated oxidation position. MnO, for instance, is fundamental. While Mn2O7 is acidic because they are ionic, oxides at less oxidation states are base. Because they are covalent, compounds at greater forms of oxidation are acidic.
(ii) Since oxygen & fluorine are tiny, relatively electronegative components with the highest oxidizing properties, a transition metal has greater oxidation modes in oxides & fluorides. Vanadium has an oxidation temperature of +5 in V2O5, while osmium exhibits an oxidation value of +6 in O5F6.
(iii) The greatest degree of oxidation is found in oxo metallic anions, such as Cr in Cr2O72-, which has an oxidation stage of +6, and Mn in MnO4-, which has an oxidation position of +7. Once more, this results from the metal’s interaction with oxygen, a powerful oxidizer and strong electronegative.
4.26

Ans – (i)

(ii)

4.27

Ans – A uniform combination of several metals or non-metal substances is called a metal alloy. Misch metal is a cerium (Ce) alloy. Iron (Fe), neodymium (Nd), lanthanum (La), and minor quantities of aluminium, sulphur, and carbon, among other elements. Jet engine components are made with it.
4.28

📌 Key Points to Note from Question
Key Concept:
- Inner Transition Elements: Lanthanides (Z = 57-71) and Actinides (Z = 89-103)
- These elements have electrons filling the f-orbitals (4f or 5f series)
Ans – Inner-transition components are f-block features where the final electron reaches the f-sub shell. They consist of actinoids (Z=90 to 103) & lanthanoids (Z=58 to 71). Therefore, the interior transition components are those that have atomic no. of 59, 95 & 102.
4.29

📌 Key Points to Note from Question
Key Concept:
- Lanthanoids show a stable +3 oxidation state with limited variability (+2, +4 in some cases).
- Actinoids exhibit a wider range of oxidation states (+3 to +7) due to 5f-orbitals’ poor shielding and higher electrostatic interactions.
Ans – Lanthanoids exhibit only three oxidation states: +2, +3 & +4 (with +3 being probably the most prevalent). The significant energy difference between the 4f, 5d, and 6s subshells is the source of instability. Actinoids exhibit a variety of oxidation types. However, their predominant oxidation level is + 3. For instance, uranium (Z = 92) & plutonium (Z – 94) exhibit + 3, + 4, + 5 and + 6, neptunium (Z = 94) displays + 3, +4, + 5 and + 7 respectively. The following is due to the little power differential among the actinoids’ 5f, 6d & 7s orbital elements.
4.30

Ans – Lawrencium (Z = 103) is the last actinoid.
Electronic configuration will be [Rn]86 5f14 6d1 7s2
The possible state of oxidation is +3.
4.31

Ans –

4.32

Ans – +4 oxidation state: 58Ce, 59Pr, 65Tb, +2 oxidation state: 60Nd, 62Sm, 63Eu, 69Tm, 70Yb.
Materials possessing the structure 5d06s2 often display the +2 oxidation level, which makes it easy to lose 2 electrons. In a similar way elements that shed 4 electrons and gain an arrangement that is either near 4f0 or 4f7 exhibit the +4 oxidation condition.
4.33

Ans – (i) Electronic arrangement: Actinoids have continuously occupied 5f-orbitals, while lanthanoids have consistently occupied 4f-orbitals.
(ii) Oxidation reads as follows: The oxidation state of lanthanoids is +3. Additionally, multiple substances exhibit +2 & +4 oxidation states. The oxidation levels of actinoids are +3, +4, +5, +6, and +7. Even so, the more popular ones are +3 and +4.
(iii) Chemical responsiveness: Because actinoids have larger atoms and smaller ionization energies than lanthanoids, they have a greater reactive.
4.34

Ans –

4.35

Ans – (i) Electronic arrangement: Overall, the electronic configurations of each component in a single vertical row are identical. There are just 2 outliers to the initial transition sequence. Namely Cr = 3d5 4s1 & Cu = 3d10 4s1. However, there are more exemptions in the subsequent transition sequence, such as Y = 4d1 5s2, Nb = 4d1 5s1, Mo = 4d5 5s1, Ru = 4d1 5s1, Rh = 4d8 5s1, Pd = 4d10 5s°, and Ag = 4d10 5s1. Pt = 5d9 6s1 & Au = 5d10 6s1 are the 2 outliers to the 3rd phase. As a result, the electrical arrangement of each part of 3 groups is not always comparable in an identical vertical section.
(ii) Oxidation condition: In broad terms, the oxidation states of each element in the identical transverse column are comparable. The substances in the center of each sequence display the most forms of oxidation, while the ones at the extremes display the fewest.
(iii) Enthalpies of ionization: Although there are occasional outliers in every region, the initial ionization enthalpies in every series typically rise progressively as we proceed from left to right. Several components of the second (4d) series have greater initial ionization energy values than the constituents of the third family in the identical vertical column, while others have less than values than average ones. The 3rd (5d) series’ initial ionization energy levels. Nevertheless, are greater in comparison to those of the 3d & Ad families. This results from the nucleus’s modest insulation by 4f-electrons in the series of 5d arrangement.
(iv) Atomic dimensions: Although the drop is relatively slight, ions with identical charge levels or atoms in a certain series often exhibit an ongoing reduction in circumference as the atomic number rises. However, due to lanthanoid shrinkage, the dimension of the constituent parts of the 5d family is almost equal to that of the Ad sequence, while the atoms of the Ad category are bigger than the equivalent components of the 3d species.
4.36

Ans –

4.37

Ans – The 4th (4d), fifth (5d) & sixth (6d) transition sequences are where the stronger transition components are found. For several causes, their characteristics ought to vary from those of the components in the initial (3d) collection:
(i) The substances in the Ad & 5d series have bigger atomic radii because they possess larger outer electron shells. Even so, due to lanthanoid contraction, the disparity between the Ad and 5d transitional components is relatively smaller.
(ii) The components of the Ad and 5d series have greater m.p. and b.p. due to tighter interatomic bonds.
(iii) Once we proceed from a single sequence to the next, ionization enthalpies should drop. Yet, because of lanthanoid contractions, the probabilities for each component in the 5d categories are greater than those of the remaining 2 categories.
As a result, the nominal nuclear charge rises while the dimension of an atomic particle shrinks. In the scenario of 3D components, this leads to a rise in ionization power.
4.38

Ans –

(i) K4[Mn(CN)6] In this compound, Mn exhibits a +2 oxidation state and a μ of 2.2 BM. This indicates that it possesses only one unpaired electron. As CN– ligands approach the Mn2+ ion, the electrons in the 3d orbital undergo pairing.

Therefore, CN– acts as a strong ligand. The hybridisation is d2sp3, resulting in an inner-orbital octahedral complex.
(ii) [Fe(H2O)6]2+:- In this compound, Fe exhibits a +2 oxidation state and a μ of 5.3 BM. This indicates that there are 4 unpaired electrons in 3d. Also 3d electrons do not pair up when the H2O molecules approach. Thus H2O is a weak ligand.

The hybridisation is sp3d2, resulting in an outer-orbital octahedral complex.
(iii) K2[MnCl4] In this compound, Mn exhibits a +2 oxidation state and a μ of 5.92 BM. This indicates that it possesses 5 unpaired electrons.

The hybridisation is sp3, resulting in tetrahedral complex. Cl is a weak ligand
Related Study Resources of Chapter 4 – The D and F Block Elements
Students can use the links below to get extra study materials for Class 12 Chemistry Chapter 4: The D and F Block Elements
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1 | Class 12 Chemistry Chapter 4 The D and F Block Elements- Important Questions |
NCERT Solutions for Class 12 The D and F Block Elements
Inorganic chemistry depends much on the d- and f-block elements. These elements show properties not like those of the s- and p-block elements. Covering all Intext and Exercise Questions, this page offers D and F Block Elements Class 12 NCERT Solutions, thereby enabling the students to acquire vital ideas efficiently to enable good test preparation.
Class 12 Chemistry Chapter 4 explains d and f block elements. These are transition and inner transition metals. Electronic configurations, oxidation states, and chemical properties are explained for transition elements, which show variable valency, catalytic behavior, and colored ion formation. Lanthanides and actinides have a different kind of trend: atomic size shows contraction. It is important for the understanding of metal chemistry and its industrial importance. Solutions at NCERT provided here are giving detailed answers to all the Intext and Exercise Questions, thus making exam preparation easier and structured.
Exceeding your Class 12 chemistry curriculum requires mastery of the ideas D and F block elements provide. The NCERT answers for the intext questions and exercises will help you to increase your knowledge and let you pass your tests. To properly base your knowledge in this part of chemistry, practise often and get assistance if needed.
FAQ Section
NCERT questions make it clear to students the fundamental concepts, upon which lie the basic questions in the board exams. It helps students practice better and score higher marks.
Electrons are easily lost in variable numbers as there is small energy difference between ns and (n-1)d orbitals.
It is the progressive decrease in atomic and ionic radii of lanthanides down the series due to poor shielding by 4f electrons.
Due to d-d electron transitions in the presence of ligands, they absorb certain wavelengths of light, giving colors.
Used in catalysts (Fe, Pt, V2O5), construction materials (Fe, Cu, Zn), and electrical applications (Ag, Cu).