d and f-Block Elements Quiz

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Questions and Answers

Which characteristic of transition elements contributes to their strong metallic bonding?

  • The presence of one or two labile $ns^1$ or $ns^2$ electrons. (correct)
  • Their oxidation states.
  • The absence of unpaired electrons.
  • The presence of paired $d$ electrons.

Why do Cr, Mo, and W exhibit high hardness among transition metals?

  • Due to their low enthalpy of atomization.
  • Due to the large number of unpaired electrons that strengthens bonding. (correct)
  • Due to their smaller atomic radii.
  • Due to the absence of $d$ electrons.

What factor contributes to the relatively lower hardness of Zn, Cd, and Hg compared to other transition metals?

  • The presence of unpaired electrons, leading to strong overlap.
  • They have very high enthalpy of atomization.
  • The absence of unpaired electrons, resulting in weaker metallic bonding. (correct)
  • The presence of $f$ electrons.

How do the ionization energies of transition elements compare to those of s-block and p-block elements?

<p>Higher than s-block elements but lower than p-block elements. (A)</p> Signup and view all the answers

What is the primary reason for the gradual increase in ionization energy across a transition series?

<p>Increase in nuclear charge. (C)</p> Signup and view all the answers

Why is the increase in ionization energy not very significant across the period of d-block elements?

<p>Due to the screening effect of the gradually filling $(n-1) d$-orbitals. (B)</p> Signup and view all the answers

What accounts for the higher ionization energies of 5d-transition elements compared to 3d- and 4d-transition elements?

<p>Ineffective shielding of the nucleus by 4f-electrons. (C)</p> Signup and view all the answers

What information can be estimated from the magnitude of ionization energy values of transition elements?

<p>The relative stabilities of various oxidation states of metals. (D)</p> Signup and view all the answers

What causes the color in transition metal complexes?

<p>Absorption of specific wavelengths of visible light for d-d electronic transitions. (C)</p> Signup and view all the answers

Why do d-orbitals split into different energy levels in transition metal complexes?

<p>Under the influence of the ligands attached to the metal ion. (C)</p> Signup and view all the answers

Which electronic configuration would typically result in a colorless complex?

<p>d¹⁰ (B)</p> Signup and view all the answers

What is the relationship between absorbed and transmitted light in colored complexes?

<p>Absorbed and transmitted light together constitute white light. (B)</p> Signup and view all the answers

In the complex ion $[Ti(H₂O)₆]^{3+}$, why does it appear violet?

<p>It absorbs yellow light and transmits violet light. (D)</p> Signup and view all the answers

What determines whether a transition metal complex will exhibit color?

<p>The ability of electrons to undergo d-d transitions. (B)</p> Signup and view all the answers

What is the relative energy of $e_g$ orbitals compared to $t_{2g}$ orbitals in an octahedral complex?

<p>$e_g$ orbitals have higher energy than $t_{2g}$ orbitals. (A)</p> Signup and view all the answers

Why are $Zn^{2+}$ salts white?

<p>They have filled d-orbitals which prevent d-d transitions. (B)</p> Signup and view all the answers

What occurs after the d⁵ configuration in d-orbitals?

<p>Paired electrons in d-orbitals begin to experience repulsive interactions. (C)</p> Signup and view all the answers

What causes the elements of the second and third transition series to have similar atomic radii?

<p>The effects of lanthanide contraction. (C)</p> Signup and view all the answers

How are the variable oxidation states of transition metals primarily determined?

<p>From the participation of ns and (n-1)d electrons in bonding. (D)</p> Signup and view all the answers

What is a characteristic feature of complex compounds formed by transition elements?

<p>They link metal ions with molecules/ions through co-ordinate bonds. (D)</p> Signup and view all the answers

What contributes to the tendency of transition metals to form complexes?

<p>A high charge density and small size of their ions. (D)</p> Signup and view all the answers

What is one reason that transition metal compounds are usually colored?

<p>They have partially filled d-orbitals that allow for electron transitions. (B)</p> Signup and view all the answers

In which type of bonding do ligands participate when forming complex compounds with transition metals?

<p>Co-ordinate bonding (B)</p> Signup and view all the answers

Why do transition metal ions have large effective nuclear charges?

<p>Because of their higher atomic numbers and resulting electrostatic forces. (C)</p> Signup and view all the answers

Why are Ni(II) compounds thermodynamically more stable than Pt(II) compounds?

<p>The sum of the first two ionization energies is lower for nickel. (A)</p> Signup and view all the answers

What does a smaller value of total enthalpy change, ∆HT, indicate about a metal's oxidation state in solution?

<p>Greater stability of the oxidation state. (B)</p> Signup and view all the answers

What factor influences the stability of a metal's oxidation state in aqueous solution alongside ionization energy?

<p>Enthalpy of sublimation. (A)</p> Signup and view all the answers

As the atomic number increases in the first transition series, what trend is observed in atomic radii?

<p>Atomic radii decrease, remain constant, then increase. (A)</p> Signup and view all the answers

What primarily causes the decrease in atomic radii at the beginning of the transition series?

<p>Screening effect of d-orbital electrons. (D)</p> Signup and view all the answers

In the context of transition metals, how do standard electrode potentials affect oxidation state stability?

<p>Smaller standard electrode potentials indicate greater stability. (D)</p> Signup and view all the answers

Which of the following factors does NOT influence the total enthalpy change, ∆HT?

<p>State of oxidation of the metal. (B)</p> Signup and view all the answers

Which compound is known to exist for platinum in the +4 oxidation state?

<p>K₂PtCl₆ (C)</p> Signup and view all the answers

Why is Cu2+ more stable than Cu+ in an aqueous solution?

<p>Cu2+ has a higher hydration energy due to its small size and greater charge (D)</p> Signup and view all the answers

What causes CuI2 to be highly unstable?

<p>Cu2+ oxidizes iodide ion (I-) to I2 (C)</p> Signup and view all the answers

What is the primary cause of the lanthanide contraction?

<p>Ineffective shielding of f-orbital (B)</p> Signup and view all the answers

What is the result of the lanthanide contraction on the basic character of hydroxides?

<p>Decrease in basic character (C)</p> Signup and view all the answers

Which ion has the highest stability in aqueous solution among Mn3+, Cr3+, and Ti3+?

<p>Cr3+ due to its half-filled t2g3 orbital (D)</p> Signup and view all the answers

Why is platinum(IV) more stable than nickel(IV)?

<p>The sum of the first four ionisation energies for nickel is higher than for platinum (A)</p> Signup and view all the answers

Which of the following statements accurately describes the ions of actinoids?

<p>They are radioactive (D)</p> Signup and view all the answers

Which transition metal exhibits the largest number of oxidation states?

<p>Manganese since it has seven electrons available for bonding (B)</p> Signup and view all the answers

What distinguishes silver as a transition element despite its filled d-orbitals?

<p>It has an incomplete d-orbital in a higher oxidation state (A)</p> Signup and view all the answers

Which ion is a stronger reducing agent: Cr2+ or Fe2+?

<p>Cr2+ due to its oxidation to a more stable Cr3+ (C)</p> Signup and view all the answers

Why do lanthanides show similar properties among themselves across periods?

<p>Due to the lanthanide contraction (A)</p> Signup and view all the answers

Which of the following elements is a notable exception to non-radioactivity in lanthanides?

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

Why are transition metal oxides basic in their lowest oxidation state and acidic in their highest oxidation state?

<p>Low oxidation states form ions while high states form covalent bonds (D)</p> Signup and view all the answers

Why do transition elements commonly form colored compounds?

<p>They have unpaired electrons that allow for color absorption (B)</p> Signup and view all the answers

How does the metallic radius change across the transition elements from Sc to Cu?

<p>It shows a small and irregular decrease (A)</p> Signup and view all the answers

What property distinguishes transition elements from zinc, cadmium, and mercury?

<p>They have incomplete d-orbitals (A)</p> Signup and view all the answers

Flashcards

Transition elements

Metals with partially filled d-orbitals allowing metallic bonding.

Metallic bonding

Bonding due to overlapping of unpaired electrons in metals.

Enthalpy of atomization

Energy required to break the attractions between atoms in a substance.

Soft metals

Metals like Zn, Cd, and Hg with weaker metallic bonding due to fewer unpaired electrons.

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Ionization energy

Energy required to remove an electron from an atom.

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Nuclear charge

The total charge of the nucleus affecting electron shielding and ionization energy.

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Effective nuclear charge

Actual charge felt by an electron after accounting for screening by other electrons.

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Oxidation state stability

Indication of how stable a particular oxidation state of a metal is based on ionization energy.

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Ionization Energy of Nickel vs. Platinum

Nickel (Ni) has a lower sum of first two ionization energies than platinum (Pt), making Ni(II) more stable than Pt(II).

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Stability of Pt(IV) vs. Ni(IV)

Platinum (Pt) has a lower sum of first four ionization energies than nickel (Ni), making Pt(IV) more stable than Ni(IV).

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K₂PtCl₆

A well-known compound of platinum in the +4 oxidation state, while the corresponding nickel compound is not known.

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Factors Determining Stability in Solutions

The stability of a metal state in solutions is determined by ionization energy, enthalpy of sublimation, and lattice/solvation energies.

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Total Enthalpy Change Equation (∆HT)

The total enthalpy change (∆HT) is the sum of sublimation enthalpy, ionization energy, and hydration enthalpy: ∆HT = ∆HS + I.E. + ∆Hhyd.

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Stability and Total Enthalpy Change

A smaller value of total enthalpy change (∆HT) indicates greater stability of a metal's oxidation state in solution.

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Electrode Potential (E°red) Relation

A smaller standard electrode potential (E°red) corresponds to a more stable oxidation state of a metal in aqueous solution.

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Atomic and Ionic Radii Trends

In transition elements, atomic radii decrease, then stay constant, and finally increase across a period due to nuclear charge and electron effects.

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d-orbital pairing

Pairing of electrons in d-orbitals after d⁵ configuration, affected by electron repulsion.

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Ionic radii trends

Ionic radii of transition metals generally increase towards the end of periods due to repulsion and lanthanide contraction.

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Lanthanide contraction

Effect causing the atomic radii of second and third transition series to be nearly equal due to poor shielding of f-electrons.

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Variable oxidation states

Transition metals exhibit multiple oxidation states due to involvement of ns and (n-1)d electrons in bonding.

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Lower oxidation state

Generally shown when only ns-electrons participate in bonding, less energy needed.

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Complex compounds

Compounds containing a metal ion bonded to surrounding anions or neutral molecules via coordinate bonds.

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Ligands

Ions or molecules that donate electron pairs to form coordinate bonds with a central metal atom.

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Color of transition-metal compounds

Transition metal compounds are typically colored due to electronic transitions within d-orbitals.

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Colour of Transition Compounds

The colour is due to absorption of visible light for electron promotion.

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d-Orbital Splitting

d-orbitals split into two sets (eg and t2g) under ligand influence.

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Electron Transition

Electrons move from lower to higher d-orbitals within the same subshell.

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Visible Light Absorption

Energy needed for electron transition is in the visible light region.

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Complimentary Color

The emitted colour of a complex is the complementary color of the absorbed light.

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Example: Titanium Salts

Titanium salts are purple due to d¹ electron absorbing yellow light.

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Zn²⁺ and Ti⁴⁺ Salts

They are white because they do not absorb visible light; full or vacant d-orbitals.

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Unpaired Electrons

Presence of unpaired electrons in partially filled d-orbitals allows d-d transitions.

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Effect on reducing agents

Lanthanide contraction decreases the tendency of elements to act as reducing agents due to increased bond strength.

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Basic character of hydroxides

Lanthanide contraction leads to decreased basicity of hydroxides as size decreases and bond strength increases.

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Color of ions

Lanthanides form mostly colorless ions while actinides form colored ions.

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Complex formation

Actinides can easily form complexes while lanthanides do not.

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Radioactivity

Most actinides are radioactive, while lanthanides (except promethium) are not.

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d and f block electronic configuration

Transition elements have partially filled d-orbitals; f-block elements have f-orbitals filling sequentially.

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Transition element definition

Silver is a transition element despite filled d-orbitals due to its incomplete d-orbital in higher oxidation state.

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Stability of Cu2+

Cu2+ is more stable than Cu+ due to high hydration energy from its small size and higher charge.

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Instability of CuI2

CuI2 is unstable because Cu2+ oxidizes iodide ions (I-) to I2.

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Unpaired Electrons in Ions

Mn3+, Cr3+, and Ti3+ have unpaired electrons; Cr3+ is most stable due to half-filled t2g3 orbital.

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Scandium Oxidation States

Scandium does not show variable oxidation states as it achieves a stable inert gas configuration by losing three electrons.

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Oxidation States of Manganese

Manganese exhibits the largest number of oxidation states due to having seven valence electrons in its d and s orbitals.

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Reducing Agents: Cr2+ vs Fe2+

Cr2+ is a stronger reducing agent than Fe2+ because it oxidizes to a stable Cr3+ state with half-filled orbitals.

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Acidity of Metal Oxides

Lowest oxidation states of transition metals are basic while highest states are acidic due to bond types formed.

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Study Notes

d and f-Block Elements

  • The periodic table is divided into four blocks (s, p, d, and f) based on the orbital where the last electron enters.
  • Transition elements (d-block) are found in periods 4 and onwards and are elements with a partially filled d-orbital
  • The d-block elements exhibit a transition between the s- and p-block elements.
  • The d-block elements generally contain partially filled orbitals (except Zn, Cd, and Hg)
  • The f-block consists of the lanthanides and actinides
  • Lanthanides (4f-series) and Actinides (5f-series) show similar properties due to lanthanide contraction
  • Transition elements are hard, lustrous, malleable, ductile, and have high melting and boiling points; and are good conductors of heat and electricity
  • Transition elements have variable oxidation states.
  • Transition metals form many coloured compounds.
  • Transition elements have high enthalpy of atomization
  • Transition elements (especially those with unpaired electrons) form interstitial compounds
  • Transition elements act as good catalysts.

Electronic Configuration of d-block elements

  • Electronic configuration of d block elements: (n-1)d1-10ns1-2
  • Electronic configuration of f block elements: (n-2)f1-14(n-1)d0-1ns0-2

Exceptional Configurations of Cr and Cu

  • Chromium (Cr) and Copper (Cu) have anomalous electronic configurations to achieve greater stability by half-filled or fully-filled d-orbitals.
  • The greater stability of half-filled and fully filled d-orbitals is due to high exchange energy.

Metallic Character

  • The metallic character of transition elements generally decreases across a series
  • Ionization energy increases gradually across a period. The relative difference in ionization energy between consecutive d-block elements is much smaller compared to s and p block elements.
  • The energy required to increase the oxidation state of the transition elements increases gradually.
  • Transition elements exhibit variable oxidation states due to the participation of ns and (n-1)d electrons in bonding.
  • The variable oxidation states of transition elements is due to the participation of ns and (n-1)d electrons in bonding.
  • The lower oxidation state is generally exhibited when ns electrons participate in bonding and higher oxidation states are shown when both ns and (n-1)d electrons participate in bonding together.
  • Transition metal ions generally form coloured compounds in solution.

Complex Formation

  • Complex compounds are compounds where a metal ion is linked to a number of anions or neutral molecules called ligands through coordinate bonds.
  • The tendency to form complexes is greater in transition metals due to their small size and high charge density, vacant orbitals and large effective nuclear charge.

Atomic and Ionic Radii

  • Atomic radii of transition elements lie between those of s and p block elements and first decrease, then remain almost constant, and then increase across the period
  • This pattern is due to the increasing nuclear charge and the effect of the screening of d electrons. In the case of the lanthanides (4f electron filling) the atomic radii continuously decrease which is known as Lanthanide Contraction.

Oxidation States

  • Transition metals exhibit a wide variety of oxidation states.
  • The variable oxidation states are due to the participation of ns and (n-1)d electrons in bonding.

Other Properties

  • Alloy formation: The similar atomic sizes of transition elements allow one element to take positions in another's crystal lattice
  • Catalytic properties: Transition metals act as catalysts due to their ability to form unstable intermediate complex with reactants and the availability of empty d-orbitals
  • Interstitial compounds: Atoms of hydrogen, carbon, and nitrogen fill the spaces within the lattice of transition metals.
  • Magnetic properties: Transition metals are often paramagnetic due to unpaired electrons.

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