Question 1

Which of the following best explains why the absorption spectrum of [Ni(H$$_2O$$)$$_6$$]$$^{2+}$$ shows three distinct bands in the visible region?

Accepted Answer

The three bands arise from d-d transitions between split $$t_{2g}$$ and $$e_g$$ orbitals in an octahedral field.

Question 2

Why does the absorption spectrum of [Ni(en)$$_3$$]$$^{2+}$$ shift to higher energy compared to [Ni(H$$_2O$$)$$_6$$]$$^{2+}$$?

Accepted Answer

Ethylenediamine is a stronger field ligand than water, increasing $$\Delta_o.$$

Question 3

What is the Jahn-Teller effect?

Accepted Answer

A distortion of non-linear molecules in degenerate electronic states to lower symmetry and energy.

Question 4

For the complex [V(H$$_2O$$)$$_6$$]$$^{3+}$$, if $$Dq/B = 3.0$$ and $$B = 600 cm$^{-1}$$, what is the value of $$Dq$$?

Accepted Answer

$$Dq = 1800 cm$^{-1}$$

Question 5

Given $$Dq = 1800 cm$^{-1}$$ for [V(H$$_2O$$)$$_6$$]$$^{3+}$$, what is the value of $$\Delta_o$$?

Accepted Answer

$$\Delta_o = 10Dq = 18000 cm$^{-1}$$

Question 6

What is the ground state free atom term for a d$$^2$$ ion such as V$$^{3+}$$?

Accepted Answer

$$^3F$$

Question 7

Which of the following is a spin-allowed transition for a d$$^2$$ octahedral complex?

Accepted Answer

$$^3T_1g \$$rightarrow ^3$$T_2g$$

Question 8

For the Cr$$^{3+}$$ ion in [Cr(H$$_2O$$)$$_6$$]$$^{3+}$$, if $$
u_1$ = 17000 cm$^{-1}$$, $$
u_2$ = 24000 cm$^{-1}$$, and $$
u_3$ = 37000 cm$^{-1}$$, which equation would you use to solve for $$B$$ and $$\Delta_o$$?

Accepted Answer

Use the Tanabe-Sugano diagram equations for d$$^3$$ ions relating $$
u_1$, $$\$$nu_2$$, $$
u_3$ to B$ and $$\Delta_o$$.

Question 9

Which of the following statements about the Tanabe-Sugano diagram for d$$^3$$ ions is correct?

Accepted Answer

It allows the calculation of $$B$$ and $$\Delta_o$$ from experimental transition energies.

Question 10

Which of the following best describes why [Ni(en)$$_3$$]$$^{2+}$$ absorbs at higher energy than [Ni(H$$_2O$$)$$_6$$]$$^{2+}$$?

Accepted Answer

The ligand field strength of en is greater than that of H$$_2O$$, increasing $$\Delta_o.$$

Question 11

Which of the following is NOT a consequence of the Jahn-Teller effect?

Accepted Answer

Increase in the number of unpaired electrons.

Question 12

Which transition is typically observed in the visible region for a d$$^3$$ octahedral complex?

Accepted Answer

$$^4A_{2g} \$$rightarrow ^4$$T_{2g}$$

Question 13

If $$\Delta_o$$ increases for a transition metal complex, what happens to the wavelength of maximum absorption ($$\lambda_{max}$$)?

Accepted Answer

$$\lambda_{max}$$ decreases (shifts to shorter wavelength)

Question 14

Which of the following is a correct statement about the effect of ligand field strength on the color of transition metal complexes?

Accepted Answer

Stronger field ligands cause absorption at higher energy, resulting in a color shift toward the blue.

Question 15

Which of the following is the correct ground state term symbol for a free Cr$$^{3+}$$ ion (d$$^3$$)?

Accepted Answer

$$^4F$$

Transition Metal Complexes: Spectra, Crystal Field Theory, and Term Symbols

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