Chemistry d- and f- Block Elements

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Questions and Answers

What causes paramagnetism in transition metal compounds?

The absence of all electrons

The orbital angular momentum alone

Unpaired electrons with associated magnetic moments (correct)

The presence of paired electrons

In the first series of transition metals, what is the significance of orbital angular momentum in relation to magnetic moments?

It is the sole contributor to magnetic moments

It is effectively quenched and has no significance (correct)

It only affects magnetic moments in solid-state compounds

It has a significant effect on magnetic moments

How is the magnetic moment ( extmu) for unpaired electrons calculated using the 'spin-only' formula?

μ = n (n + 2) (correct)

μ = n (n + 1)

μ = n²

μ = n (n - 2)

What is the magnetic moment of a single unpaired electron in units of Bohr magneton?

1.73 Bohr magnetons (BM) Signup and view all the answers

How does the number of unpaired electrons affect the observed magnetic moment?

The magnetic moment increases with the number of unpaired electrons Signup and view all the answers

Which transition metal exhibits oxidation states ranging from +2 to +7?

Manganese Signup and view all the answers

Which of the following statements best describes why scandium and titanium have lesser oxidation states?

They are at the beginning of the series with limited electrons to share. Signup and view all the answers

Among the following metals, which has an oxidation state of +2 as its only common oxidation state?

Zinc Signup and view all the answers

What is the maximum oxidation state manganese can achieve?

+7 Signup and view all the answers

Which transition metal's oxidation states are primarily influenced by the presence of d electrons?

Copper Signup and view all the answers

What can be inferred about the stability of higher oxidation states as you move across the transition metal series?

They gradually decrease in stability after manganese. Signup and view all the answers

Which statement is true regarding titanium's oxidation states?

Titanium is more stable in Ti(IV) than in Ti(II) or Ti(III). Signup and view all the answers

What is the common reason for the limited oxidation states of transition metals at the series extremes?

Excess d electrons limit sharing possibilities. Signup and view all the answers

What is the calculated value of the spin-only magnetic moment for the M2+ ion (Z = 27)?

4.8 BM Signup and view all the answers

What does the color of a transition metal ion in solution correspond to?

The complementary color of the light absorbed Signup and view all the answers

Which of the following transition metal ions is likely to absorb light in the visible region?

Cu2+ Signup and view all the answers

What primarily determines the frequency of light absorbed by a transition metal ion in solution?

The nature of the ligand Signup and view all the answers

Which transition metal ion is arranged in the following order in terms of color in aqueous solutions: V4+, V3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+?

From violet to green Signup and view all the answers

What factor influences the contraction in ionic radii observed in the series of elements?

Imperfect shielding of one electron by another within the same sub-shell Signup and view all the answers

How does the shielding of 4f electrons compare to that of d electrons?

4f electrons shield less effectively than d electrons Signup and view all the answers

What trend is observed in the sizes of the elements with increasing atomic number?

Regular decrease in sizes Signup and view all the answers

What is the implication of increased nuclear charge on the ionic radii in this series?

It causes a consistent decrease in ionic radii Signup and view all the answers

Which of the following elements shows a 4+ oxidation state in this series?

Ce Signup and view all the answers

What is the phenomenon called that describes the decrease in atomic radii from the 4d to the 5d series?

Lanthanoid contraction Signup and view all the answers

Which of the following elements exhibits similar atomic radii due to lanthanoid contraction?

Zr and Hf Signup and view all the answers

What causes the lanthanoid contraction?

Imperfect shielding of electrons Signup and view all the answers

What is the relationship between the radii of the 4d and 5d series as atomic numbers increase?

The 5d series radii are almost the same as those of the 4d series. Signup and view all the answers

Which orbitals must be filled before the 5d series can begin?

4f orbitals Signup and view all the answers

The physical and chemical properties of the 4d and 5d series are more similar than typically expected because of what?

Their similar atomic radii Signup and view all the answers

How are the atomic sizes of the 3d, 4d, and 5d series compared overall?

Atomic sizes increase from 3d to 4d, then remain constant to 5d. Signup and view all the answers

What does the term 'imperfect shielding' refer to in the context of lanthanoid contraction?

Electrons in the same set of orbitals fail to fully shield the nucleus. Signup and view all the answers

What does the lanthanoid contraction cause in terms of ionic radii?

It leads to similar radii for the third transition series and the corresponding second series members. Signup and view all the answers

Which pair of elements illustrates the effect of lanthanoid contraction?

Zr and Hf Signup and view all the answers

What oxidation states are predominantly found in lanthanoids?

+3 and +4 Signup and view all the answers

Why is the formation of Ce(IV) favored despite its oxidizing nature?

Because of its noble gas configuration. Signup and view all the answers

What is the standard reduction potential (E°) for the Ce/Ce4+ reaction?

+1.74 V Signup and view all the answers

Which of the following states accurately describes the stability of +2 and +4 ions in lanthanoids?

Their occurrence is rare and irregular. Signup and view all the answers

What characteristic of Zr and Hf complicates their separation in nature?

Their almost identical ionic radii. Signup and view all the answers

Which factors contribute to the irregularities observed in the ionization enthalpies of lanthanoids?

Electronic configurations of the ions. Signup and view all the answers

Study Notes

Objectives

Learn the positions of d- and f-block elements in the periodic table
Understand the electronic configurations of transition (d-block) and 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 important compounds like K2Cr2O7 and KMnO4
Understand the general characteristics of d- and f-block elements, and horizontal and group trends
Describe the properties of f-block elements; compare lanthanoids and actinoids regarding configurations, oxidation states, and chemical behavior

d- and f- Block Elements

Iron, copper, silver, and gold are significant transition elements, historically important
Inner transition elements (Th, Pa, U) are crucial for nuclear energy
The d-block elements (groups 3-12) have progressively filling d orbitals in each of the four long periods
The f-block elements have progressively filling 4f and 5f orbitals
Transition metals and inner transition metals are often used to refer to elements in the d- and f-blocks
There are four series of transition metals: 3d (Sc to Zn), 4d (Y to Cd), 5d (La to Hg), and 6d (Ac to Cn)
Inner transition metals include lanthanoids (Ce to Lu) and actinoids (Th to Lr)

Electronic Configurations

General electronic configuration of the outer orbitals of d-block elements is (n-1)d¹-10ns¹-2, except for Pd (4d¹º5sº).
The (n-1) represents inner d orbitals, which can have 1 to 10 electrons
The outermost ns orbital can have 1 or 2 electrons
Exceptions like Cr (3d⁵4s¹) and Cu (3d¹⁰4s¹) exist due to the stability of half-filled and completely filled orbitals
Zn, Cd, and Hg in group 12 have full d¹⁰ configurations, hence are not transition elements

Physical Properties

Most transition elements are hard, have high melting and boiling points, and low volatility
High melting and boiling points are due to involvement of (n-1)d electrons in metallic bonding
Melting points are at their maximum around the middle of the series
High enthalpies of atomisation are from strong interatomic interaction

Atomic and Ionic Sizes

Atomic and ionic radii generally decrease across a given series due to increasing nuclear charge and poor shielding by d electrons
The lanthanoid contraction is a significant decrease in atomic radii from La to Lu due to poor shielding by 4f electrons causing similar physical and chemical properties in the second and third series of transition elements

Oxidation States

The transition elements exhibit a wide variety of oxidation states due to the involvement of d orbitals
The highest oxidation numbers in oxides and fluorides are frequent, with progressively decreasing trend towards lower oxidation states at the end of the series
The lowest common oxidation state is usually +2; higher oxidation states are commonly observed in oxides and other compounds, especially for elements in the middle of the series
Unusual cases of Cr and Cu are observed where +1 and /or +3 are not typically expected

Catalytic Properties

Transition metals are often catalysts due to their ability to adopt multiple oxidation states and form complexes (e.g., V₂O₅ as catalyst in Contact Process)

Interstitial Compounds

Interstitial compounds (e.g., TiC, Mn₄N) form when small atoms (H, C, N) are trapped inside the crystal lattice of metals, exhibiting hardness, high melting points, and chemical inertness

Alloy Formation

Alloys of transition metals are often hard and have high melting points
Alloys are readily formed due to similar atomic radii and other characteristics
Examples include steel, brass, and bronze

Important Compounds

Potassium dichromate (K₂Cr₂O₇) and potassium permanganate (KMnO₄) are important compounds of transition metals.

Formation of Complex Compounds

Transition metals form a large number of complex compounds due to small size, high ionic charges, and availability of d orbitals for bond formation
Examples include [Fe(CN)₆]³⁻, [Fe(CN)₆]⁴⁻, [Cu(NH₃)₄]²⁺, and [PtCl₄]²⁻

Inner Transition Elements

Lanthanoids (14 elements following La) and actinoids (14 elements following Ac)
Lanthanoid and actinoid contraction are due to poor shielding of 4f and 5f electrons, leading to similar properties in the second and third series of transition elements
Actinoids display more varied chemical behavior and many are radioactive
Oxidation state of +3 is common for lanthanoids;
Oxidation states vary even more widely in actinoids

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Description

Explore the intricate world of d- and f-block elements in this quiz. Understand their positions in the periodic table, electronic configurations, and oxidation states. Additionally, delve into the properties and uses of notable compounds such as K2Cr2O7 and KMnO4.