Trends and Properties of 3d Transition Metals

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Questions and Answers

What general trend is associated with the less negative $E^\ominus$ values observed in the series of elements from Ti to Zn?

Decrease in atomic radii
Increase in the number of unpaired d-electrons
Decrease in hydration enthalpies
Increase in the sum of the first and second ionization enthalpies (correct)

Why is $Cr^{2+}$ reducing in nature?

It achieves a half-filled $t_{2g}$ level after oxidation to $Cr^{3+}$ (correct)
It achieves a fully filled $t_{2g}$ level after oxidation
It forms stronger bonds in the oxidized state
It gains more electrons upon oxidation

Why does the change from $Mn^{3+}$ to $Mn^{2+}$ result in extra stability?

It gains more electrons, increasing nuclear shielding.
It achieves a fully filled $d$ orbital configuration.
It achieves a half-filled $d^5$ configuration. (correct)
It loses two electrons, reducing electron-electron repulsion.

Given that the $E^\ominus (M^{2+}/M)$ value for copper is positive (+0.34V), which combination of factors most likely contributes to this unusual characteristic compared to other first-row transition metals?

High enthalpy of atomization and low hydration enthalpy (A) Signup and view all the answers

Suppose a hitherto unknown transition metal, 'X', exhibits a significantly more negative $E^\ominus (X^{2+}/X)$ value than any other element in the first transition series. Assuming typical thermochemical behavior except where noted, which scenario would most plausibly explain this extreme negativity, considering that $∆aH$ is the enthalpy of atomization and $∆{hyd}H$ is the hydration enthalpy?

X has a moderately high $∆aH$ and a $∆{hyd}H$ near zero or positive value. (A) Signup and view all the answers

Which factor primarily accounts for the irregular variation in first and second ionization enthalpies across the first transition series?

Varying stability of different electronic configurations. (D) Signup and view all the answers

What is a characteristic of the chemical reactivity of transition metals?

Wide variation in reactivity, from dissolving in mineral acids to being 'noble'. (B) Signup and view all the answers

Why are titanium and vanadium passive to dilute, non-oxidizing acids at room temperature?

Their reaction rates with hydrogen ions are inherently slow. (D) Signup and view all the answers

What general trend is observed in the $E^V$ values ($M^{2+}$/M) across the first transition series?

A consistent decrease in negative values. (C) Signup and view all the answers

How is the trend in $E^V$ values related to ionization enthalpies?

Related to the sum of the first and second ionization enthalpies. (D) Signup and view all the answers

Which electronic configuration primarily contributes to the unexpected $E^V$ value of manganese (Mn)?

$d^5$ (D) Signup and view all the answers

What accounts for the unexpectedly negative $E^V$ value of nickel (Ni)?

Highest negative enthalpy of hydration. (C) Signup and view all the answers

Consider three transition metals: Manganese (Mn), Nickel (Ni), and Zinc (Zn). Which of the following statements accurately describes the factors influencing their $E^V$ values?

Mn's $E^V$ is related to its $d^5$ stability, Ni's to its hydration enthalpy, and Zn's to its $d^{10}$ stability. (B) Signup and view all the answers

Which characteristic of transition elements is most directly attributed to their partially filled d orbitals?

Display of a variety of oxidation states (C) Signup and view all the answers

Why are the d orbitals of transition elements more influenced by their surroundings compared to s or p orbitals?

They protrude to the periphery of the atom more. (C) Signup and view all the answers

What is a key difference in property trends between transition and non-transition elements?

Transition elements show greater horizontal similarity in properties compared to non-transition elements. (D) Signup and view all the answers

Which statement correctly relates electronic configuration to the classification of an element as a transition element?

An element with a partially filled d orbital in its ground state or common oxidation state is a transition element. (B) Signup and view all the answers

Why is zinc not considered a transition element, despite being in the d-block?

Zinc's d orbitals are completely filled in both its ground state and common oxidation states. (C) Signup and view all the answers

Consider two hypothetical transition metals, Element X and Element Y. Element X has a $d^3$ configuration in its +2 oxidation state, while Element Y has a $d^{10}$ configuration in its +2 oxidation state. Based on this information, which of the following statements is most likely to be true?

Element X is more likely to exhibit catalytic activity compared to Element Y. (D) Signup and view all the answers

Element Q exhibits a unique property: in its +3 oxidation state, it forms a complex ion with six cyanide ligands ($CN^−$), resulting in a diamagnetic complex. Knowing that $CN^−$ is a strong-field ligand, and assuming the complex has an octahedral geometry, what can be inferred about the electronic configuration of Element Q in its +3 oxidation state within the complex?

The electronic configuration is $t_{2g}^6 e_g^0$, indicating no unpaired electrons. (A) Signup and view all the answers

A researcher discovers a novel transition metal complex with the formula $[M(L)_4]^{2+}$, where M is the transition metal ion, and L is a newly synthesized neutral ligand. Spectroscopic analysis reveals that the complex is paramagnetic with two unpaired electrons. X-ray diffraction data indicates that the complex has a perfect tetrahedral geometry. Given this information and assuming that L is neither a strong field nor a weak field ligand, which of the following is the most plausible electron configuration for the metal M in this complex?

$e^2 t_2^2$ (A) Signup and view all the answers

What is the calculated magnetic moment (in Bohr magnetons, BM) for $Sc^{3+}$?

0 BM (D) Signup and view all the answers

Which of the following ions is expected to exhibit the highest 'spin only' magnetic moment?

$Cr^{2+}$ (A) Signup and view all the answers

The observed magnetic moment for $Fe^{2+}$ is in the range of 5.3 - 5.5 BM. What factor primarily accounts for the difference between the calculated (spin-only) value of 4.90 BM and the observed value?

Orbital contribution to the magnetic moment. (A) Signup and view all the answers

What d-electron configuration is associated with the $M^{2+}$ ion (Z=27)?

$3d^7$ (C) Signup and view all the answers

Calculate the 'spin only' magnetic moment of $M^{2+}$ (aq) ion (Z = 27).

3.87 BM (A) Signup and view all the answers

Which of the following statements accurately describes the relationship between the electronic configuration and the color of transition metal ions?

The color arises from $d-d$ transitions, where electrons move between different $d$ orbitals. (C) Signup and view all the answers

An aqueous solution of a divalent transition metal ion appears green. Which statement provides the most accurate explanation for this observation?

The ion absorbs red light, transmitting the complementary color. (C) Signup and view all the answers

Consider two aqueous solutions: one containing $Co^{2+}$ and another containing $Ni^{2+}$. Based on the provided data, devise an experimental procedure, using only a spectrophotometer and the data in Table 8.7, to unambiguously identify which solution contains which ion without using any additional chemical reagents or known standards.

Measure the magnetic susceptibility of both solutions. The solution with a magnetic moment closer to 4.4 - 5.2 BM is likely $Co^{2+}$. (D) Signup and view all the answers

Why is the formation of $Ce^{4+}$ favored, despite its strong oxidizing nature?

It achieves a noble gas configuration, enhancing stability. (A) Signup and view all the answers

Which of the following lanthanides is described as exhibiting behavior similar to europium?

Samarium (D) Signup and view all the answers

What accounts for the formation of $Eu^{2+}$?

The loss of its two s electrons leads to a stable $f^7$ configuration. (B) Signup and view all the answers

Given that $Ce^{4+}$ has a standard reduction potential ($E^o$) of $+1.74$ V, why is it still used as an analytical reagent despite being capable of oxidizing water?

The high overpotential of oxygen evolution kinetics limits the reaction rate making it useful in titrations. (C) Signup and view all the answers

If a researcher discovers a new lanthanide element (hypothetical element 'X') that predominantly exists in the +2 oxidation state and exhibits strong reducing properties transitioning to +3, drawing parallels with known lanthanides, which electron configuration of $X^{2+}$ would most likely account for this behavior?

$[Xe]4f^{6}5d^{0}6s^{0}$ (striving for a half-filled f-shell configuration via oxidation) (A) Signup and view all the answers

What causes the diamagnetism observed in permanganate ions?

The absence of unpaired electrons due to molecular orbital interactions. (B) Signup and view all the answers

What happens when potassium permanganate ($KMnO_4$) is heated to 513 K?

It decomposes into $K_2MnO_4$, $MnO_2$, and $O_2$. (D) Signup and view all the answers

Which of the following statements accurately describes the role of hydrogen ion concentration in reactions involving permanganate?

The hydrogen ion concentration significantly influences the reaction, as demonstrated in the half-reactions. (A) Signup and view all the answers

Which of the following CANNOT be directly oxidized by acidified permanganate solution?

Manganate to permanganate (A) Signup and view all the answers

Given the following half-reactions and their standard reduction potentials ($E^o$), which species is the strongest oxidizing agent under standard conditions?

$MnO_4^- + e^- \rightarrow MnO_4^{2-}$ $E^o$ = +0.56 V $MnO_4^- + 4H^+ + 3e^- \rightarrow MnO_2 + 2H_2O$ $E^o$ = +1.69 V $MnO_4^- + 8H^+ + 5e^- \rightarrow Mn^{2+} + 4H_2O$ $E^o$ = +1.52 V

$MnO_4^-$ (in acidic solution) (D) Signup and view all the answers

Why does the reaction between permanganate and water proceed extremely slowly at [H+] = 1, despite the redox potential suggesting it should occur?

The activation energy for the reaction is very high, resulting in slow kinetics. (A) Signup and view all the answers

A solution containing $I^-$ ions is titrated with acidified $KMnO_4$. Which of the following statements accurately describes the initial color change observed during the titration before the endpoint is reached?

The purple color of $MnO_4^-$ disappears immediately upon addition to the $I^-$ solution. (C) Signup and view all the answers

Consider a scenario where acidified $KMnO_4$ is used to oxidize $Fe^{2+}$ to $Fe^{3+}$. However, an unknown substance $X$ is introduced, which reacts rapidly with $Fe^{3+}$ to regenerate $Fe^{2+}$. How would this affect the overall titration, and what would be observed?

The endpoint would be significantly delayed, requiring much more $KMnO_4$ to achieve a persistent pink color. (D) Signup and view all the answers

Flashcards

d-orbital characteristic properties

Elements with partially filled d orbitals exhibit variable oxidation states, colored ions, complex formation, catalytic properties, and paramagnetism.

Horizontal similarities

Transition elements in the same horizontal row exhibit more similarities compared to non-transition elements.