Chemistry d- and f- Block Elements
39 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

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?

<p>1.73 Bohr magnetons (BM) (A)</p> Signup and view all the answers

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

<p>The magnetic moment increases with the number of unpaired electrons (D)</p> Signup and view all the answers

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

<p>Manganese (D)</p> Signup and view all the answers

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

<p>They are at the beginning of the series with limited electrons to share. (D)</p> Signup and view all the answers

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

<p>Zinc (C)</p> Signup and view all the answers

What is the maximum oxidation state manganese can achieve?

<p>+7 (C)</p> Signup and view all the answers

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

<p>Copper (A)</p> 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?

<p>They gradually decrease in stability after manganese. (A)</p> Signup and view all the answers

Which statement is true regarding titanium's oxidation states?

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

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

<p>Excess d electrons limit sharing possibilities. (D)</p> Signup and view all the answers

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

<p>4.8 BM (B)</p> Signup and view all the answers

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

<p>The complementary color of the light absorbed (D)</p> Signup and view all the answers

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

<p>Cu2+ (A)</p> Signup and view all the answers

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

<p>The nature of the ligand (C)</p> 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+?

<p>From violet to green (A)</p> Signup and view all the answers

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

<p>Imperfect shielding of one electron by another within the same sub-shell (D)</p> Signup and view all the answers

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

<p>4f electrons shield less effectively than d electrons (C)</p> Signup and view all the answers

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

<p>Regular decrease in sizes (A)</p> Signup and view all the answers

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

<p>It causes a consistent decrease in ionic radii (B)</p> Signup and view all the answers

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

<p>Ce (C)</p> 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?

<p>Lanthanoid contraction (D)</p> Signup and view all the answers

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

<p>Zr and Hf (A)</p> Signup and view all the answers

What causes the lanthanoid contraction?

<p>Imperfect shielding of electrons (C)</p> Signup and view all the answers

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

<p>The 5d series radii are almost the same as those of the 4d series. (D)</p> Signup and view all the answers

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

<p>4f orbitals (C)</p> 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?

<p>Their similar atomic radii (B)</p> Signup and view all the answers

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

<p>Atomic sizes increase from 3d to 4d, then remain constant to 5d. (C)</p> Signup and view all the answers

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

<p>Electrons in the same set of orbitals fail to fully shield the nucleus. (D)</p> Signup and view all the answers

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

<p>It leads to similar radii for the third transition series and the corresponding second series members. (D)</p> Signup and view all the answers

Which pair of elements illustrates the effect of lanthanoid contraction?

<p>Zr and Hf (C)</p> Signup and view all the answers

What oxidation states are predominantly found in lanthanoids?

<p>+3 and +4 (C)</p> Signup and view all the answers

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

<p>Because of its noble gas configuration. (C)</p> Signup and view all the answers

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

<p>+1.74 V (A)</p> Signup and view all the answers

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

<p>Their occurrence is rare and irregular. (D)</p> Signup and view all the answers

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

<p>Their almost identical ionic radii. (D)</p> Signup and view all the answers

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

<p>Electronic configurations of the ions. (A), Presence of f subshell electrons. (D)</p> Signup and view all the answers

Flashcards

Oxidation State

The charge an atom appears to have when combined with other atoms.

Transition Metal Oxidation State Trend

The elements in the middle of the transition metal series exhibit the greatest variety of oxidation states.

Oxidation State of Early Transition Metals

Elements like scandium (Sc) and titanium (Ti) have fewer electrons to lose or share, resulting in limited oxidation states.

Oxidation State of Late Transition Metals

Elements like copper (Cu) and zinc (Zn) have a large number of d electrons, leading to fewer orbitals available for sharing, limiting their oxidation states.

Signup and view all the flashcards

Maximum Oxidation State

The highest oxidation state of reasonable stability corresponds to the sum of s and d electrons, up to manganese.

Signup and view all the flashcards

Stability of Higher Oxidation States

The stability of higher oxidation states decreases abruptly after manganese.

Signup and view all the flashcards

Iron Oxidation States

The most common oxidation states for iron are +2 and +3.

Signup and view all the flashcards

Zinc Oxidation State

Zinc only has one common oxidation state, +2.

Signup and view all the flashcards

Paramagnetism

A property of substances with unpaired electrons, causing them to be attracted to a magnetic field.

Signup and view all the flashcards

Magnetic Moment and Unpaired Electrons

The magnetic moment of a substance is determined by the number of unpaired electrons it possesses.

Signup and view all the flashcards

Spin-Only Formula

A formula calculating the magnetic moment considering only the spin of electrons, ignoring the contribution of orbital angular momentum.

Signup and view all the flashcards

Bohr Magneton (BM)

The unit used to measure magnetic moment, representing the magnetic moment of a single electron.

Signup and view all the flashcards

Magnetic Moment as a Tool

The measured magnetic moment is a useful indicator of the number of unpaired electrons present in an atom, molecule, or ion.

Signup and view all the flashcards

Lanthanoid Contraction

The reduction of atomic radii observed across the lanthanide series. This contraction counteracts the typical increase in atomic size expected with increasing atomic number.

Signup and view all the flashcards

How does Lanthanoid Contraction happen?

The filling of 4f orbitals before 5d orbitals in the lanthanide series leads to a decrease in atomic size, effectively minimizing the expected size increase due to the addition of electron shells.

Signup and view all the flashcards

What is a consequence of Lanthanoid Contraction?

The similar atomic radii observed in corresponding elements of the second (4d) and third (5d) transition series. This similarity is due to the lanthanoid contraction.

Signup and view all the flashcards

How does Lanthanoid Contraction affect properties?

Similar chemical and physical properties in elements belonging to the second (4d) and third (5d) transition series. This similarity is attributed to the nearly identical atomic radii caused by the lanthanoid contraction.

Signup and view all the flashcards

What causes Lanthanoid Contraction (in simple terms)?

The shielding effect within a set of orbitals is not perfect - electrons in the same set of orbitals do not completely shield each other from the nucleus.

Signup and view all the flashcards

Why do the sizes of elements in the 2nd and 3rd transition series become similar?

The atomic radii of elements in the third (5d) transition series are nearly the same as those in the second (4d) series, unlike the expected increase seen in normal group trends. This effect is caused by the lanthanoid contraction.

Signup and view all the flashcards

Explain the impact of 4f orbital filling on the 5d series.

The filling of 4f orbitals before 5d orbitals in the lanthanide series leads to a decreased size of subsequent elements, which is a key factor affecting the properties of the second and third transition series.

Signup and view all the flashcards

Summarize the impact of Lanthanoid Contraction on periodic trends.

The similar atomic radii of corresponding elements within the second and third transition series lead to similar physical and chemical properties, defying typical trends.

Signup and view all the flashcards

d-Orbital Excitation

The process of an electron transitioning from a lower energy d orbital to a higher energy d orbital within a transition metal ion.

Signup and view all the flashcards

Energy of Excitation

The energy difference between the lower and higher d orbitals in a transition metal ion, which corresponds to the frequency (and color) of light absorbed.

Signup and view all the flashcards

Complementary Color

The observed color of a transition metal ion solution is complementary to the color of light it absorbs.

Signup and view all the flashcards

Ligand Influence on Color

The nature of the ligands surrounding a transition metal ion influences the energy difference between d orbitals, affecting the color absorbed and observed.

Signup and view all the flashcards

Color in Transition Metal Ions

The unique colors of transition metal ions in solutions are due to the excitation of d electrons and the subsequent absorption of light.

Signup and view all the flashcards

Ionic Radii Trend in Lanthanides

The ionic radii of lanthanides generally decrease with increasing atomic number. This is due to the increasing nuclear charge, which pulls the electrons closer to the nucleus.

Signup and view all the flashcards

Lanthanide Contraction vs. Transition Metal Contraction

The decrease in ionic radii across the lanthanide series is less pronounced than the decrease in transition metal series.

Signup and view all the flashcards

Cause of Lanthanide Contraction

The decrease in ionic radii across the lanthanides is attributed to the imperfect shielding of 4f electrons by other 4f electrons, leading to a stronger effective nuclear charge.

Signup and view all the flashcards

Regular Decrease in Lanthanide Ionic Radii

The lanthanide series exhibits a steady decrease in ionic radii as atomic number increases. This is because the increasing nuclear charge pulls the electrons in tighterdespite the incomplete shielding of 4f electrons.

Signup and view all the flashcards

What is Lanthanoid Contraction?

The gradual decrease in atomic radii observed across the Lanthanide series (elements 57 to 71). It's caused by the poor shielding effect of the 4f electrons on the outer electrons.

Signup and view all the flashcards

How does Lanthanoid Contraction affect atomic size?

The Lanthanoid Contraction results in almost identical atomic radii for elements in the second (4d) and third (5d) transition series. This is because the 4f electrons in the Lanthanides 'contract' the size of the next series.

Signup and view all the flashcards

What's the impact of similar sizes on elements?

The similar sizes caused by the Lanthanoid Contraction lead to remarkably similar chemical and physical properties for elements in the 2nd and 3rd transition series.

Signup and view all the flashcards

What's special about Lanthanides oxidation states?

While the Lanthanides (elements 57 to 71) often exhibit a +3 oxidation state, some can also have +2 or +4 oxidation states. These unusual states happen because of the extra stability of empty, half-filled, or full f orbitals.

Signup and view all the flashcards

How does Cerium's oxidation state work?

Cerium (Ce) is an example; it can be in the +4 oxidation state due to its full f orbital configuration. But it's a strong oxidant, meaning it tends to lose that extra electron and return to the common +3 state.

Signup and view all the flashcards

What does Ce^4+/Ce^3+ potential tell us?

The standard reduction potential (E°) for the Ce^4+/Ce^3+ couple is +1.74 V, suggesting it can oxidize water. This means it's a very strong oxidant.

Signup and view all the flashcards

What happens to higher oxidation states after manganese?

The stability of higher oxidation states (like +4, +5, etc.) decreases rapidly after manganese. It's because the d electrons are getting more shielded and it becomes harder to remove them.

Signup and view all the flashcards

Why does Lanthanoid Contraction happen?

The filling of 4f orbitals before 5d orbitals in the Lanthanide series results in a weaker shielding effect, causing the 5d electrons to be pulled closer to the nucleus.

Signup and view all the flashcards

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

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Transition Elements (d-Block) PDF

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.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser