Define degenerate orbitals .

Degenerate orbitals are orbitals that are equal in energy. In an isolated transition element ion, all five 3d orbitals are degenerate.

What causes the 3d orbitals to split into non-degenerate sets?

When ligands form dative bonds with the central metal ion, the lone pairs of the ligands repel the d orbital electrons by different amounts depending on orbital orientation, causing the five d orbitals to split into two sets of unequal energy.

True or False? In an octahedral complex, the 3d x 2 -y 2 and 3d z 2 orbitals are at a lower energy than the other three d orbitals.

False. In an octahedral complex, the 3d x 2 -y 2 and 3d z 2 orbitals are at a higher energy because they point along the axes where the ligands approach, causing greater repulsion.

In an octahedral complex, the ligands approach along the .......... , causing greater repulsion with the .......... and 3d z 2 orbitals.

In an octahedral complex, the ligands approach along the x, y and z axes , causing greater repulsion with the 3d x 2 -y 2 and 3d z 2 orbitals.

Define non-degenerate orbitals .

Non-degenerate orbitals are orbitals that are not equal in energy. In a transition element complex, ligand bonding splits the five 3d orbitals into two sets of non-degenerate orbitals.

In a tetrahedral complex, which set of d orbitals is at higher energy after splitting?

In a tetrahedral complex, the 3d yz , 3d xz and 3d xy orbitals are at higher energy because the ligand bonding pairs align with these orbitals, causing greater repulsion.

True or False? The energy gap between the two sets of non-degenerate d orbitals is labelled ΔE.

True. The energy difference between the two sets of non-degenerate d orbitals in a complex is called Δ*E *.

An isolated transition element ion has .......... degenerate d orbitals. When ligands bind, these split into .......... sets of non-degenerate orbitals.

An isolated transition element ion has five degenerate d orbitals. When ligands bind, these split into two sets of non-degenerate orbitals.

Why do the 3d x 2 -y 2 and 3d z 2 orbitals experience more repulsion from ligands in an octahedral complex?

These two orbitals have lobes pointing along the x, y and z axes — the same directions from which the six ligands approach. Their electrons are therefore closer to the bonding electrons of the ligands, causing more repulsion.

Define complementary colour .

A complementary colour is the colour observed from a transition element complex — it is made up of the wavelengths of visible light that are not absorbed by the complex.

Why do transition element complexes appear coloured?

Ligands cause the d orbitals to split into non-degenerate sets. Electrons absorb light of a specific frequency (equal to ΔE) and are promoted to a higher energy orbital. The complementary colour — the frequencies not absorbed — is what we observe.

True or False? Changing the ligand on a transition metal complex can change the colour of the complex, even if the oxidation state of the metal remains the same.

True. Different ligands split the d orbitals by different amounts of energy (different ΔE), so a different frequency of light is absorbed, resulting in a different complementary colour.

The equation relating energy absorbed to frequency is ΔE = .......... × .......... , where h is Planck's constant.

The equation relating energy absorbed to frequency is ΔE = h × ν , where h is Planck's constant.

What colour change occurs when ammonia ligands replace water ligands in [Cu(H 2 O) 6 ] 2+ ?

The complex changes from light blue ([Cu(H 2 O) 6 ] 2+ ) to dark blue ([Cu(NH 3 ) 4 (H 2 O) 2 ] 2+ ) because the ammonia ligands split the d orbitals by a different ΔE.

True or False? [Co(H 2 O) 6 ] 2+ is pink and [Co(NH 3 ) 6 ] 2+ is brown.

True. The change from water to ammonia ligands alters ΔE and therefore the frequency of light absorbed, causing the observed colour to change from pink to brown .

Define electron promotion .

Electron promotion is the process in which an electron in a transition metal complex absorbs light energy equal to ΔE and jumps from a lower to a higher non-degenerate d orbital.

Why does [Cu(H 2 O) 4 (OH) 2 ] appear pale blue while [CuCl 4 ] 2- appears yellow?

The chloride ligands split the d orbitals by a different ΔE compared to water and hydroxide. This changes the frequency of light absorbed, so the complementary colour observed shifts from pale blue to yellow .

Copper(II) ions absorb light from the .......... end of the spectrum, so the observed colour is .......... .

Copper(II) ions absorb light from the red end of the spectrum, so the observed colour is pale blue (cyan) .

A LevelChemistryCambridge (CIE)Flashcards28. Chemistry of Transition ElementsColour of Complexes

Colour of Complexes (Cambridge (CIE) A Level Chemistry): Flashcards

Exam code: 9701

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FrontDegenerate & non-Degenerate d Orbitals
Define degenerate orbitals.

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Cards in this collection (18)

Define degenerate orbitals.
Degenerate orbitals are orbitals that are equal in energy. In an isolated transition element ion, all five 3d orbitals are degenerate.
What causes the 3d orbitals to split into non-degenerate sets?
When ligands form dative bonds with the central metal ion, the lone pairs of the ligands repel the d orbital electrons by different amounts depending on orbital orientation, causing the five d orbitals to split into two sets of unequal energy.
True or False?
In an octahedral complex, the 3d_x²_-y² and 3d_z² orbitals are at a lower energy than the other three d orbitals.
False. In an octahedral complex, the 3d_x²_-y² and 3d_z² orbitals are at a higher energy because they point along the axes where the ligands approach, causing greater repulsion.
In an octahedral complex, the ligands approach along the .........., causing greater repulsion with the .......... and 3d_z² orbitals.
In an octahedral complex, the ligands approach along the x, y and z axes, causing greater repulsion with the 3d_x²_-y² and 3d_z² orbitals.
Define non-degenerate orbitals.
Non-degenerate orbitals are orbitals that are not equal in energy. In a transition element complex, ligand bonding splits the five 3d orbitals into two sets of non-degenerate orbitals.
In a tetrahedral complex, which set of d orbitals is at higher energy after splitting?
In a tetrahedral complex, the 3d_yz, 3d_xz and 3d_xy orbitals are at higher energy because the ligand bonding pairs align with these orbitals, causing greater repulsion.
True or False?
The energy gap between the two sets of non-degenerate d orbitals is labelled ΔE.
True. The energy difference between the two sets of non-degenerate d orbitals in a complex is called Δ*E*.
An isolated transition element ion has .......... degenerate d orbitals. When ligands bind, these split into .......... sets of non-degenerate orbitals.
An isolated transition element ion has five degenerate d orbitals. When ligands bind, these split into two sets of non-degenerate orbitals.
Why do the 3d_x²_-y² and 3d_z² orbitals experience more repulsion from ligands in an octahedral complex?
These two orbitals have lobes pointing along the x, y and z axes — the same directions from which the six ligands approach. Their electrons are therefore closer to the bonding electrons of the ligands, causing more repulsion.
Define complementary colour.
A complementary colour is the colour observed from a transition element complex — it is made up of the wavelengths of visible light that are not absorbed by the complex.
Why do transition element complexes appear coloured?
Ligands cause the d orbitals to split into non-degenerate sets. Electrons absorb light of a specific frequency (equal to ΔE) and are promoted to a higher energy orbital. The complementary colour — the frequencies not absorbed — is what we observe.
True or False?
Changing the ligand on a transition metal complex can change the colour of the complex, even if the oxidation state of the metal remains the same.
True. Different ligands split the d orbitals by different amounts of energy (different ΔE), so a different frequency of light is absorbed, resulting in a different complementary colour.
The equation relating energy absorbed to frequency is ΔE = .......... × .........., where h is Planck's constant.
The equation relating energy absorbed to frequency is ΔE = h × ν, where h is Planck's constant.
What colour change occurs when ammonia ligands replace water ligands in [Cu(H₂O)₆]²⁺?
The complex changes from light blue ([Cu(H₂O)₆]²⁺) to dark blue ([Cu(NH₃)₄(H₂O)₂]²⁺) because the ammonia ligands split the d orbitals by a different ΔE.
True or False?
[Co(H₂O)₆]²⁺ is pink and [Co(NH₃)₆]²⁺ is brown.
True. The change from water to ammonia ligands alters ΔE and therefore the frequency of light absorbed, causing the observed colour to change from pink to brown.
Define electron promotion.
Electron promotion is the process in which an electron in a transition metal complex absorbs light energy equal to ΔE and jumps from a lower to a higher non-degenerate d orbital.
Why does [Cu(H₂O)₄(OH)₂] appear pale blue while [CuCl₄]^2- appears yellow?
The chloride ligands split the d orbitals by a different ΔE compared to water and hydroxide. This changes the frequency of light absorbed, so the complementary colour observed shifts from pale blue to yellow.
Copper(II) ions absorb light from the .......... end of the spectrum, so the observed colour is ...........
Copper(II) ions absorb light from the red end of the spectrum, so the observed colour is pale blue (cyan).

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