| Date | November 2021 | Marks available | 3 | Reference code | 21N.2.hl.TZ0.9 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | 9 | Adapted from | N/A |
Question
Fast moving helium nuclei (4He2+) were fired at a thin piece of gold foil with most passing undeflected but a few deviating largely from their path. The diagram illustrates this historic experiment.
Figure from PPLATO / FLAP (Flexible Learning Approach To Physics), http://www.met.reading.ac.uk/pplato2/h-flap/
phys8_1.html#top 1996 The Open University and The University of Reading.
Suggest what can be concluded about the gold atom from this experiment.
Subsequent experiments showed electrons existing in energy levels occupying various orbital shapes.
Sketch diagrams of 1s, 2s and 2p.
State the electron configuration of copper.
Copper is a transition metal that forms different coloured complexes. A complex [Cu(H2O)6]2+ (aq) changes colour when excess Cl− (aq) is added.
Explain the cause of this colour change, using sections 3 and 15 from the data booklet.
Markscheme
Most 4He2+ passing straight through:
most of the atom is empty space
OR
the space between nuclei is much larger than 4He2+ particles
OR
nucleus/centre is «very» small «compared to the size of the atom» ✔
Very few 4He2+ deviating largely from their path:
nucleus/centre is positive «and repels 4He2+ particles»
OR
nucleus/centre is «more» dense/heavy «than 4He2+ particles and deflects them»
OR
nucleus/centre is «very» small «compared to the size of the atom» ✔
Do not accept the same reason for both M1 and M2.
Accept “most of the atom is an electron cloud” for M1.
Do not accept only “nucleus repels 4He2+ particles” for M2.
1s AND 2s as spheres ✔
one or more 2p orbital(s) as figure(s) of 8 shape(s) of any orientation (px, py pz) ✔
1s22s22p63s23p64s13d10
OR
[Ar] 4s13d10 ✔
Accept configuration with 3d before 4s.
chloride is lower in the spectrochemical series ✔
«ligand cause» decreased/lesser splitting «in d-orbitals compared to H2O» ✔
frequency/energy of light absorbed is decreased
OR
wavelength of light absorbed is increased ✔
Accept ·chloride a weaker ligand than water/produces a smaller energy difference than water for M1.
Award [2 max] for mentioning splitting of orbitals is changed AND frequency/ wavelength/energy of light absorbed
are different/changed without mentioning correct decrease or increase.
Examiners report
Syllabus sections
-
22M.1.hl.TZ1.8:
Why is hydrated copper (II) sulfate blue?
A. Blue light is emitted when electrons return to lower d-orbitals.
B. Light complimentary to blue is absorbed when electrons return to lower d-orbitals.
C. Blue light is emitted when electrons are promoted between d-orbitals.
D. Light complimentary to blue is absorbed when electrons are promoted between d-orbitals.
-
17N.1.hl.TZ0.10:
[CoCl6]3– is orange while [Co(NH3)6]3+ is yellow. Which statement is correct?
A. [CoCl6]3– absorbs orange light.
B. The oxidation state of cobalt is different in each complex.
C. The different colours are due to the different charges on the complex.
D. The different ligands cause different splitting in the 3d orbitals.
-
22M.1.hl.TZ2.8:
[Cr(OH2)6]3+ is violet and [Cr(NH3)6]3+ is yellow. What is correct?
The Colour Wheel
- 18M.1.hl.TZ1.8: Which complex has the greatest d orbital splitting?
- 18M.1.hl.TZ2.8: Part of the spectrochemical series is shown for transition metal complexes. I−< Cl− <...
-
19M.3.hl.TZ1.3b(i):
Identify the colour of the emission spectrum of lithium using section 17 of the data booklet.
- 19M.1.hl.TZ2.6: How is colour produced in transition metal complexes? A. Light is absorbed when electrons...
-
17M.2.hl.TZ2.2b.iii:
Explain why iron forms many different coloured complex ions.
-
18N.3.hl.TZ0.1c:
Copper(II) ion solutions are blue. Suggest, giving your reason, a suitable wavelength of light for the analysis.
-
19N.2.hl.TZ0.6f(iv):
Examine the relationship between the Brønsted–Lowry and Lewis definitions of a base, referring to the ligands in the complex ion [CuCl4]2−.
-
19N.2.hl.TZ0.6f(ii):
Deduce why the Cu(I) solution is colourless.
-
19N.2.hl.TZ0.6f(i):
Describe how the blue colour is produced in the Cu(II) solution. Refer to section 17 of the data booklet.
-
16N.1.hl.TZ0.9:
The oxidation state of cobalt in the complex ion [Co(NH3)5Br]x is +3. Which of the following statements are correct?
I. The overall charge, x, of the complex ion is 2+.
II. The complex ion is octahedral.
III. The cobalt(III) ion has a half-filled d-subshell.A. I and II only
B. I and III only
C. II and III only
D. I, II and III
-
16N.1.hl.TZ0.10:
What is the correct explanation for the colour of [Cu(H2O)6]2+?
A. Light is absorbed when an electron moves to a d orbital of higher energy.
B. Light is released when an electron moves to a d orbital of higher energy.
C. Light is absorbed when electrons move from the ligands to the central metal ion.
D. Light is absorbed when electrons move between d and s orbitals.
-
17M.2.hl.TZ1.2f:
Outline why transition metals form coloured compounds.
- 19N.1.hl.TZ0.8: What is the effect of a stronger ligand?
-
21M.2.hl.TZ2.2b(iv):
[Cr(OH)6]3− forms a green solution. Estimate a wavelength of light absorbed by this complex, using section 17 of the data booklet.
-
22M.2.hl.TZ1.4e:
Mg(OH)+ is a complex ion, but Mg is not regarded as a transition metal. Contrast Mg with manganese, Mn, in terms of one characteristic chemical property of transition metals, other than complex ion formation.
- 21M.2.hl.TZ1.3f: Outline why, unlike typical transition metals, zinc compounds are not coloured.
- 21M.2.hl.TZ1.3g: Transition metals like iron can form complex ions. Discuss the bonding between transition...
- 21M.1.hl.TZ2.8: Which factor does not affect the colour of a complex ion? A. temperature of the...
-
19M.2.hl.TZ1.6b:
Explain why, when ligands bond to the iron ion causing the d-orbitals to split, the complex is coloured.
-
21M.2.hl.TZ2.2b(iii):
Deduce, giving a reason, which complex ion [Cr(CN)6]3− or [Cr(OH)6]3− absorbs higher energy light. Use section 15 of the data booklet.
-
20N.2.hl.TZ0.6b:
The electron configuration of copper makes it a useful metal.
Explain why a copper(II) solution is blue, using section 17 of the data booklet.
- 22M.2.hl.TZ2.7d: Explain why transition metal cyanide complexes are coloured.
