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Date	November 2021	Marks available	2	Reference code	21N.2.hl.TZ0.9
Level	HL	Paper	2	Time zone	TZ0
Command term	Suggest	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.

[2]

Subsequent experiments showed electrons existing in energy levels occupying various orbital shapes.

Sketch diagrams of 1s, 2s and 2p.

[2]

b(i).

State the electron configuration of copper.

[1]

b(ii).

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.

[3]

b(iii).

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 (p_x, p_y p_z) ✔

b(i).

1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰
OR
[Ar] 4s¹3d¹⁰ ✔

Accept configuration with 3d before 4s.

b(ii).

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.

b(iii).