Mastering d- and f-Block Elements: Class 12 Chemistry Notes, Properties, and Trends Explained
The d- and f- Block Elements
8.1 Position in the Periodic Table
8.2 Electronic Configurations of the d-Block Elements
8.3 General Properties of the Transition Elements (d-Block)
8.4 Some Important Compounds of Transition Elements
8.5 The Lanthanoids
8.6 The Actinoids
8.7 Some Applications of d- and f-Block Elements
An Overview
Based on the sources provided, here is a table of contents for the unit on "The d- and f- Block Elements":
Unit 4: The d- and f- Block Elements
Objectives
- Learn the positions of the d– and f-block elements in the periodic table.
- Know the electronic configurations of the transition (d-block) and the inner transition (f-block) elements.
- Appreciate the relative stability of various oxidation states in terms of electrode potential values.
- Describe the preparation, properties, structures and uses of some important compounds such as K2Cr2O7 and KMnO4.
- Understand the general characteristics of the d– and f–block elements and the general horizontal and group trends in them.
- Describe the properties of the f-block elements and give a comparative account of the lanthanoids and actinoids with respect to their electronic configurations, oxidation states and chemical behaviour.
The Transition Elements (d-Block)
- General electronic configuration of outer orbitals: (n-1)d¹⁻¹⁰ ns¹⁻² (except Pd which is 4d¹⁰5s⁰).
- Mainly four series of transition metals: 3d series (Sc to Zn), 4d series (Y to Cd), 5d series (La and Hf to Hg), and 6d series (Ac and elements from Rf to Cn).
- 4.3 General Properties of the Transition Elements (d-Block)
- 4.3.1 Physical Properties
- High tensile strength, ductility, malleability, high thermal and electrical conductivity, metallic lustre.
- Very hard and low volatility (except Zn, Cd, Hg).
- High melting and boiling points due to involvement of (n-1)d and ns electrons in metallic bonding.
- High enthalpies of atomisation.
- Ionisation Enthalpies
- Increase from left to right due to increased nuclear charge.
- Less steep increase compared to non-transition elements.
- 4.3.4 Oxidation States
- Show a great variety of oxidation states.
- Elements near the middle of the series exhibit the greatest number of oxidation states (e.g., Manganese from +2 to +7).
- Scandium (Z = 21) does not exhibit variable oxidation states.
- 4.3.6 Trends in the M3+/M2+ Standard Electrode Potentials
- 4.3.7 Trends in Stability of Higher Oxidation States
- Fluorine and oxygen stabilize highest oxidation states.
- 4.3.8 Chemical Reactivity and Eo Values
- Many are electropositive, some are 'noble' (e.g., Cu).
- First series metals (except Cu) are generally reactive.
- 4.3.9 Magnetic Properties
- Exhibit paramagnetism (due to unpaired electrons) or diamagnetism.
- Some are ferromagnetic (extreme form of paramagnetism).
- Magnetic moment calculated by 'spin-only' formula: µ = √[n(n+2)] BM.
- 4.3.10 Formation of Coloured Ions
- Colour arises from d-d transitions (excitation of electrons within d orbitals).
- Frequency of light absorbed depends on the nature of the ligand.
- 4.3.11 Formation of Complex Compounds
- Form a large number of complex compounds.
- Interstitial Compounds
- High melting points, very hard, retain metallic conductivity, chemically inert.
- Potassium Permanganate KMnO4
- Preparation.
- Oxidizing properties (in acidic, neutral, or faintly alkaline solutions).
- Uses (analytical chemistry, preparative organic chemistry, bleaching, decolourisation).
- 4.3.1 Physical Properties
The Inner Transition Elements (f-Block)
- Consists of lanthanoids and actinoids.
- Placed in a separate panel at the bottom of the periodic table.
- 4.5 The Lanthanoids
- Fourteen elements from Ce to Lu.
- 4.5.1 Electronic Configurations
- 4.5.2 Atomic and Ionic Sizes
- Gradual decrease in size across the series (lanthanoid contraction).
- 4.5.4 General Characteristics
- Silvery white, soft metals, tarnish rapidly in air.
- Hardness increases with atomic number.
- Melting points between 1000-1200 K (except Sm at 1623 K).
- Typical metallic structure, good conductors of heat and electricity.
- Chemical behavior: earlier members reactive like calcium, later members more like aluminium.
- Combine with hydrogen, form carbides, liberate H₂ from dilute acids, burn in halogens.
- Form oxides (M₂O₃) and basic hydroxides (M(OH)₃).
- Principal oxidation state is +3, with some exhibiting +2 and +4 states. Cerium (Z=58) is known to exhibit +4 oxidation state.
- Applications: alloy steels (mischmetall), catalysts in petroleum cracking, phosphors.
- 4.6 The Actinoids
- Fourteen elements from Th to Lr.
- Radioactive elements, especially earlier members.
- 4.6.1 Electronic Configurations
- 4.6.2 Ionic Sizes
- Gradual decrease in size (actinoid contraction), greater than lanthanoid contraction.
- 4.6.3 Oxidation States
- Exhibit a wide range of oxidation states due to comparable energies of 5f, 6d, and 7s levels.
- General +3 oxidation state.
- Maximum oxidation state increases from +4 (Th) to +7 (Np) in the first half of the series, then decreases.
- 4.6.4 General Characteristics and Comparison with Lanthanoids
- Silvery appearance, variety of structures due to irregular metallic radii.
- Highly reactive metals, especially when finely divided.
- React with boiling water, combine with most non-metals at moderate temperatures.
- Hydrochloric acid attacks all, nitric acid forms protective oxide layers, alkalies have no action.
- Magnetic properties are more complex and values are lower than lanthanoids.
- Less smooth chemistry compared to lanthanoids due to wide range of oxidation states and radioactivity.
4.7 Some Applications of d- and f-Block Elements
- Iron and steels in construction materials.
- TiO for pigment industry, MnO₂ for dry battery cells.
- Zn and Ni/Cd in battery industry.
- Group 11 elements (Ag, Au, Cu) as coinage metals.
- Catalysts: V₂O₅ (H₂SO₄ manufacture), TiCl₄ with Al(CH₃)₃ (Ziegler catalysts for polyethylene), Iron (Haber process for ammonia), Nickel (hydrogenation of fats, polymerisation of alkynes), PdCl₂ (Wacker process).
- AgBr in photographic industry.
- Mischmetall alloy (lanthanoid metal + iron) for bullets, shell, lighter flint.
- Mixed oxides of lanthanoids as catalysts in petroleum cracking.
- Individual Ln oxides as phosphors in television screens.
The periodic table is organized into blocks based on the type of atomic orbital being filled with electrons. The d-block and f-block elements represent crucial sections of this table, known for their unique chemical and physical properties.
I. The d-Block Elements (Transition Metals)
The d-block of the periodic table comprises elements in Groups 3-12, where the d orbitals are progressively filled across four long periods. These elements are commonly referred to as transition metals.
A. Definition of Transition Metals Originally, the term "transition metals" indicated that their chemical properties were transitional between s- and p-block elements. According to IUPAC, transition metals are defined as metals that possess an incomplete d subshell either in their neutral atom or in their ions.
- Exceptions: Zinc (Zn), cadmium (Cd), and mercury (Hg) from Group 12 are not considered transition metals because they have a full d¹⁰ configuration in both their ground state and common oxidation states. However, their chemistry is often studied alongside transition metals as they are the end members of the 3d, 4d, and 5d transition series.
B. Series of Transition Metals There are four main series of transition metals:
- 3d series: Scandium (Sc) to Zinc (Zn).
- 4d series: Yttrium (Y) to Cadmium (Cd).
- 5d series: Lanthanum (La) and Hafnium (Hf) to Mercury (Hg).
- 6d series: Actinium (Ac) and elements from Rutherfordium (Rf) to Copernicium (Cn).
C. Electronic Configurations The general electronic configuration for the outer orbitals of d-block elements is (n-1)d¹⁻¹⁰ ns¹⁻².
- (n-1)d represents the inner d orbitals, which can hold one to ten electrons.
- ns represents the outermost s orbital, which can hold one or two electrons.
- Exceptions: This generalization has exceptions due to the small energy difference between (n-1)d and ns orbitals, and the enhanced stability of half-filled and completely filled orbital sets. Examples include Chromium (Cr) and Copper (Cu) in the 3d series, and Palladium (Pd) with a 4d¹⁰ 5s⁰ configuration.
D. General Characteristics of Transition Elements The presence of partly filled d orbitals makes transition elements distinct from non-transition elements.
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Physical Properties:
- Metallic Properties: Nearly all transition elements exhibit typical metallic properties such as high tensile strength, ductility, malleability, high thermal and electrical conductivity, and metallic luster.
- Structure: With the exceptions of Zn, Cd, Hg, and Mn, they typically have one or more metallic structures at normal temperatures (e.g., hcp, bcc, ccp).
- Hardness & Volatility: They are generally very hard and have low volatility, except for Zn, Cd, and Hg.
- Melting and Boiling Points: They possess high melting and boiling points. This is attributed to the involvement of a greater number of electrons from (n-1)d orbitals in addition to the ns electrons in the interatomic metallic bonding. Melting points usually peak around the d⁵ configuration (e.g., at the middle of each series), except for anomalies like Mn and Tc, and then fall regularly with increasing atomic number.
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Enthalpies of Atomisation:
- Transition elements have high enthalpies of atomisation. The maxima in enthalpy of atomisation near the middle of each series (d⁵) suggest that one unpaired electron per d orbital is particularly favorable for strong interatomic interaction. Generally, more valence electrons lead to stronger bonding.
- Metals from the second and third series tend to have greater enthalpies of atomisation than those in the first series, leading to more frequent metal-metal bonding in compounds of heavier transition metals. High enthalpies of atomisation also contribute to a metal's nobility.
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Atomic and Ionic Sizes:
- Across a given series, the radius of ions with the same charge progressively decreases with increasing atomic number. This is because each new electron enters a d orbital, and the shielding effect of d electrons is not very effective, leading to increased net electrostatic attraction between the nucleus and outermost electrons. A similar, but smaller, trend is observed for atomic radii.
- An interesting trend is observed when comparing sizes across different series: atomic radii increase from the first (3d) to the second (4d) series, but the radii of the third (5d) series are virtually the same as those of the corresponding members of the second series. This phenomenon is known as the lanthanoid contraction, which occurs due to the filling of 4f orbitals before the 5d series begins, causing a stronger nuclear charge attraction and a reduction in size.
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Ionisation Enthalpies:
- Ionisation enthalpy generally increases from left to right across each transition series due to an increase in nuclear charge as inner d orbitals are filled.
- However, the increase in successive ionisation enthalpies for transition elements is not as steep as in non-transition elements. The variation in ionisation enthalpy within a transition series is much less compared to non-transition elements across a period.
- The values show that the first ionisation enthalpy generally increases, but the magnitude of increase for the second and third ionisation enthalpies is much higher along a series. This behavior is partly explained by the varying stability of d⁰, d⁵, and d¹⁰ configurations. For example, high second and third ionization enthalpies make it difficult to achieve oxidation states greater than +2 for elements like copper, nickel, and zinc.
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Oxidation States:
- A notable characteristic of transition elements is their great variety of oxidation states in compounds.
- The elements displaying the largest number of oxidation states are typically found in or near the middle of the series, with manganese (Mn) exhibiting all states from +2 to +7.
- At the extreme ends of the series, the number of oxidation states is lower.
- Early in the series: Sc(II) is almost unknown, and Ti(IV) is more stable than Ti(III) or Ti(II) due to having too few electrons to lose or share.
- Late in the series: Elements like Cu and Zn show fewer higher valencies because they have too many d electrons, limiting available orbitals for sharing. For instance, the only oxidation state for zinc is +2, as no d electrons are involved.
- The highest oxidation states often correspond to the sum of s and d electrons up to manganese.
- Low oxidation states (like zero) are observed when the compound has ligands with π-acceptor character, as seen in Ni(CO)₄ and Fe(CO)₅ where nickel and iron have an oxidation state of zero.
- Scandium (Z=21) is a transition element that does not exhibit variable oxidation states.
- The highest oxidation states are stabilized by oxygen or fluorine due to their small size and high electronegativity, leading to the formation of stable oxides (e.g., Sc₂O₃ to Mn₂O₇) and fluorides (e.g., TiX₄, VF₅, CrF₆). As the oxidation number increases, the ionic character decreases, and acidic character becomes predominant in higher oxides (e.g., Mn₂O₇ is a covalent green oil and gives HMnO₄).
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Magnetic Properties:
- Many transition metal ions are paramagnetic.
- Paramagnetism arises from the presence of unpaired electrons. Each unpaired electron has a magnetic moment associated with its spin and orbital angular momentum. For first-series transition metals, the orbital angular momentum contribution is often quenched, so the magnetic moment is determined primarily by the number of unpaired electrons.
- The "spin-only" formula is used to calculate magnetic moment: μ = √n(n+2) BM, where n is the number of unpaired electrons and μ is the magnetic moment in Bohr magnetons (BM). A single unpaired electron has a magnetic moment of 1.73 BM.
- The magnetic moment increases with the number of unpaired electrons, providing a useful indicator of their presence.
- Diamagnetic substances are repelled by an applied magnetic field, while paramagnetic substances are attracted. Ferromagnetism is an extreme form of paramagnetism.
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Formation of Coloured Ions:
- Transition metals generally form coloured compounds.
- This property is due to the excitation of an electron from a lower energy d orbital to a higher energy d orbital (d-d transition). The energy required for this excitation corresponds to the frequency of light absorbed, which typically lies in the visible region. The observed color is the complementary colour of the light absorbed.
- The frequency of light absorbed, and thus the color, is influenced by the nature of the ligand. Examples of colored ions include purple Ti³⁺ (3d¹), blue Cr²⁺ (3d⁴), green Fe²⁺ (3d⁶), and blue Cu²⁺ (3d⁹). Ions with completely empty (d⁰) or completely filled (d¹⁰) d orbitals are typically colorless (e.g., Sc³⁺, Ti⁴⁺, Zn²⁺).
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Formation of Complex Compounds:
- Transition metals form a large number of complex compounds.
- This ability is attributed to:
- The comparatively smaller sizes of the metal ions.
- Their high ionic charges.
- The availability of d orbitals for bond formation.
- Examples include [Fe(CN)₆]³⁻, [Fe(CN)₆]⁴⁻, [Cu(NH₃)₄]²⁺, and [PtCl₄]²⁻.
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Catalytic Properties:
- Transition metals and their compounds are well-known for their catalytic activity.
- This activity is linked to their ability to adopt multiple oxidation states and their tendency to form complexes.
- Examples of their use as catalysts include:
- Vanadium(V) oxide (V₂O₅) in the Contact Process for sulfuric acid manufacture.
- Finely divided iron in Haber's Process for ammonia production.
- Nickel in catalytic hydrogenation.
- TiCl₄ with Al(CH₃)₃ (Ziegler catalysts) for polyethylene production.
- PdCl₂ in the Wacker process for oxidizing ethyne to ethanal.
- Nickel complexes in the polymerization of alkynes and other organic compounds.
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Interstitial Compounds:
- Transition metals can form interstitial compounds when small atoms (like H, C, N) are trapped in the interstitial sites of their crystal lattices.
- These compounds exhibit specific characteristics:
- High melting points, often higher than the pure metals.
- Very hard; some borides are as hard as diamond.
- Retain metallic conductivity.
- Are chemically inert.
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Alloys:
- An alloy is a blend of metals formed by mixing components.
- Transition metals are crucial in forming various alloys. Examples include:
- Iron and steels (most important construction materials), often alloyed with Cr, Mn, and Ni.
- Copper-nickel alloys for 'silver' UK coins.
- Mischmetall (a lanthanoid-iron alloy) for bullets, shells, and lighter flints.
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Chemical Reactivity:
- Transition metals vary widely in their chemical reactivity.
- Many are electropositive enough to dissolve in mineral acids.
- However, a few are "noble," meaning they are unaffected by single acids.
- Most metals of the first series, except copper, are relatively reactive and are oxidized by 1M H⁺.
- They react with non-metals like oxygen, nitrogen, sulfur, and halogens to form binary compounds.
E. Important Compounds: K₂Cr₂O₇ and KMnO₄
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Potassium Dichromate (K₂Cr₂O₇):
- Preparation: Prepared from chromite ore (FeCr₂O₄). The ore is fused with an alkali (like Na₂CO₃) in the presence of air, then acidified.
- Oxidizing Action: A strong oxidizing agent.
- In acidified solution, Cr₂O₇²⁻ is reduced to Cr³⁺ (E° = +1.33V).
- It oxidizes iodides to iodine, sulfides to sulfur, tin(II) to tin(IV), and iron(II) salts to iron(III).
- Example reaction: Cr₂O₇²⁻ + 14 H⁺ + 6 Fe²⁺ → 2 Cr³⁺ + 6 Fe³⁺ + 7 H₂O.
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Potassium Permanganate (KMnO₄):
- Preparation: Prepared by fusing manganese dioxide (MnO₂) with an alkali metal hydroxide (e.g., KOH) and an oxidizing agent like KNO₃ or air, forming dark green K₂MnO₄ (manganate ion). This manganate then disproportionates in neutral or acidic solution to permanganate (MnO₄⁻), or it can be electrolytically oxidized in alkaline solution. In the lab, Mn(II) salt is oxidized by peroxodisulphate.
- Properties: Forms dark purple (almost black) crystals.
- Oxidizing Action: A strong oxidizing agent. The reduction product of permanganate depends on the acidity of the solution.
- In acidic solutions: MnO₄⁻ is reduced to Mn²⁺ (E° = +1.52V). It oxidizes:
- Iodides to iodine.
- Fe²⁺ ions (green) to Fe³⁺ (yellow).
- Oxalate ion or oxalic acid to carbon dioxide at 333 K.
- Hydrogen sulfide to precipitated sulfur.
- Sulfurous acid or sulfite to sulfate.
- Nitrite to nitrate.
- In neutral or faintly alkaline solutions: MnO₄⁻ is typically reduced to MnO₂. It oxidizes:
- Iodide to iodate.
- Thiosulphate to sulphate.
- Manganous salts to MnO₂ (catalyzed by ZnSO₄ or ZnO).
- In acidic solutions: MnO₄⁻ is reduced to Mn²⁺ (E° = +1.52V). It oxidizes:
- Uses: Used in analytical chemistry, as an oxidant in preparative organic chemistry, and for bleaching wool, cotton, silk, and decolourizing oils.
II. The f-Block Elements (Inner Transition Metals)
The f-block elements are positioned in a separate panel at the bottom of the periodic table. They consist of the lanthanoids (4f series) and actinoids (5f series).
A. Lanthanoids (4f Series) The lanthanoids are the fourteen elements following lanthanum (Ce to Lu). Lanthanum itself is often included in discussions due to its close resemblance to the lanthanoids.
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Electronic Configurations:
- Atoms of lanthanoids generally have a 6s² configuration with variable occupancy of the 4f level.
- The tripositive ions (Ln³⁺), which represent the most stable oxidation state for all lanthanoids, have electronic configurations of the form 4fⁿ (n = 1 to 14 with increasing atomic number).
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Atomic and Ionic Sizes (Lanthanoid Contraction):
- A unique feature in lanthanoid chemistry is the overall decrease in atomic and ionic radii from lanthanum to lutetium, known as the lanthanoid contraction.
- This contraction has far-reaching consequences for the chemistry of the third transition series elements (5d series), making their atomic radii virtually the same as those of the corresponding elements in the second series.
- The shielding effect of 4f electrons is not very effective.
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Oxidation States:
- Lanthanoids primarily exhibit a +3 oxidation state.
- However, some elements can also show +2 and +4 oxidation states occasionally.
- Examples: Cerium (Ce) is known to exhibit the +4 oxidation state (4f⁰ configuration). Europium (Eu) (4f⁷) and Ytterbium (Yb) (4f¹⁴) exhibit +2 oxidation states, making them reductants because they can achieve stable half-filled or completely filled f-orbitals. Terbium (Tb) (4f⁷) can exhibit +4 and is an oxidant. Samarium (Sm) and Thulium (Tm) also occasionally show +2 oxidation states.
- The relative stability of +2, +3, and +4 oxidation states is influenced by the stability of empty (f⁰), half-filled (f⁷), and completely filled (f¹⁴) f-orbitals.
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General Characteristics:
- Physical Properties: Silvery white, soft metals that tarnish rapidly in air. Hardness increases with atomic number (samarium is steel hard). Melting points range from 1000 to 1200 K, except for samarium (1623 K). They have typical metallic structures and are good conductors of heat and electricity.
- Chemical Reactivity: Earlier members are quite reactive, similar to calcium. With increasing atomic number, they behave more like aluminum.
- They combine with hydrogen when gently heated.
- Form carbides (Ln₃C, Ln₂C₃, LnC₂) when heated with carbon.
- Liberate hydrogen from dilute acids.
- Burn in halogens to form trihalides (LnX₃).
- Form oxides (M₂O₃) and hydroxides (M(OH)₃), which are definite compounds and basic like alkaline earth metal hydroxides.
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Applications:
- Mainly used for the production of alloy steels for plates and pipes.
- Mischmetall: A well-known alloy consisting of ~95% lanthanoid metal and ~5% iron, with traces of S, C, Ca, and Al. Used in Mg-based alloys for bullets, shells, and lighter flints.
- Mixed oxides of lanthanoids are used as catalysts in petroleum cracking.
- Some individual Ln oxides serve as phosphors in television screens and other fluorescing surfaces.
B. Actinoids (5f Series) The actinoids include the fourteen elements from thorium (Th) to lawrencium (Lr). Actinium (Ac) is also typically included in discussions.
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Radioactivity: All actinoid elements are radioactive, which poses special problems in their study. Earlier members have shorter half-lives.
- Thorium (Th), Protactinium (Pa), and Uranium (U) are excellent sources of nuclear energy.
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Electronic Configurations: The electronic configurations involve the filling of 5f orbitals.
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Ionic Sizes (Actinoid Contraction):
- There is a gradual decrease in the size of atoms or M³⁺ ions across the actinoid series, similar to the lanthanoid contraction.
- However, the actinoid contraction is greater from element to element than lanthanoid contraction. This is due to the poor shielding effect of 5f electrons.
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Oxidation States:
- Actinoids exhibit a greater range of oxidation states compared to lanthanoids. This is partly because the 5f, 6d, and 7s levels are of comparable energies.
- The +3 oxidation state is general for actinoids.
- Elements in the first half of the series frequently show higher oxidation states. For example, the maximum oxidation state increases from +4 in Th to +5, +6, and +7 in Pa, U, and Np, respectively, but then decreases in subsequent elements.
- Like lanthanoids, +3 and +4 ions tend to hydrolyze.
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General Characteristics:
- Appearance and Structure: Actinoid metals are all silvery in appearance but display a variety of structures, indicating greater irregularities in metallic radii than in lanthanoids.
- Reactivity: They are highly reactive metals, especially when finely divided.
- Boiling water reacts with them to yield a mixture of oxide and hydride.
- They combine with most non-metals at moderate temperatures.
- Hydrochloric acid attacks all actinoid metals, but most are only slightly affected by nitric acid due to the formation of protective oxide layers.
- Alkalies have no action on them.
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Magnetic Properties: The magnetic properties of actinoids are more complex than those of lanthanoids. While the variation in magnetic susceptibility roughly parallels lanthanoids, actinoids generally have higher values.
C. Comparison of Lanthanoids and Actinoids
| Feature | Lanthanoids (4f series) | Actinoids (5f series) |
|---|---|---|
| Orbitals Filled | 4f orbitals | 5f orbitals |
| Radioactivity | Generally non-radioactive (except promethium) [Not explicitly stated in sources, but common knowledge.] | All are radioactive. |
| Oxidation States | Predominantly +3, with occasional +2 and +4. | Generally +3, but show a wider range of oxidation states (+4 to +7). |
| Ionic Sizes | Exhibit lanthanoid contraction (gradual decrease in size). | Exhibit actinoid contraction, which is greater than lanthanoid contraction due to poor shielding by 5f electrons. |
| Chemical Bonding | More predictable due to stable +3 state. | More complex chemistry due to variable oxidation states and radioactivity. |
| Shielding Effect | 4f electrons provide less effective shielding. | 5f electrons provide even poorer shielding compared to 4f electrons. |
Despite differences, early actinoids resemble lanthanoids in exhibiting close similarities to each other and gradual property variations that don't involve oxidation state changes. Both contractions have extended effects on the sizes and properties of succeeding elements.
III. Applications of d- and f-Block Elements
These elements and their compounds have numerous important applications:
- Construction Materials: Iron and steels are critical construction materials. Their production involves reducing iron oxides, removing impurities, and adding carbon and alloying metals like chromium (Cr), manganese (Mn), and nickel (Ni).
- Pigments: TiO₂ is used in the pigment industry.
- Batteries: MnO₂ is used in dry battery cells, while Zn and Ni/Cd are also required by the battery industry.
- Coinage: Elements of Group 11 (copper, silver, gold) are historically known as coinage metals. Modern coins, like UK 'copper' coins, are copper-coated steel, and 'silver' UK coins are a Cu/Ni alloy.
- Nuclear Energy: Inner transition elements like Thorium (Th), Protactinium (Pa), and Uranium (U) are excellent sources of nuclear energy.
- Catalysis: Many d-block metals and their compounds are essential catalysts in the chemical industry. Examples include V₂O₅, finely divided iron, nickel, TiCl₄ with Al(CH₃)₃ (Ziegler catalysts), PdCl₂, and nickel complexes.
- Photography: The photographic industry relies on the light-sensitive properties of AgBr.
- Alloys: Lanthanoid metals are used in alloys like mischmetall (a lanthanoid-iron alloy) for producing bullets, shells, and lighter flints.
- Phosphors: Some individual lanthanoid oxides are used as phosphors in television screens and similar fluorescing surfaces.
- Organic Synthesis: Potassium permanganate is a favored oxidant in preparative organic chemistry.
Analogy: Think of the periodic table as a large, organized library. The s-block and p-block elements are like the main sections, covering common subjects. The d-block elements are like a special "bridge" section in the middle, connecting these main sections. They are versatile, like a multi-tool, able to adopt many roles (oxidation states) and form diverse connections (complexes, alloys) because of their adaptable d-orbitals. The f-block elements are like a hidden, specialized annex at the very back, dealing with unique, heavy topics (radioactivity) and having distinct internal characteristics (contractions) that influence the main library's later sections.
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