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Date May 2022 Marks available 1 Reference code 22M.2.hl.TZ2.5
Level HL Paper 2 Time zone TZ2
Command term Describe Question number 5 Adapted from N/A

Question

Iron(II) disulfide, FeS2, has been mistaken for gold.

State the full electronic configuration of Fe2+.

[1]
a(i).

Explain why there is a large increase from the 8th to the 9th ionization energy of iron.

[2]
a(ii).

Calculate the oxidation state of sulfur in iron(II) disulfide, FeS2.

[1]
b.

Describe the bonding in iron, Fe (s).

[1]
c.

Markscheme

1s2 2s2 2p6 3s2 3p6 3d6

a(i).

Any two of:

IE9: electron in lower energy level
OR
IE9: more stable/full electron level ✔


IE9: electron closer to nucleus
OR
IE9: electron more tightly held by nucleus ✔


IE9: less shielding by «complete» inner levels ✔

a(ii).

–1 ✔

 

Accept “– I”.

b.

electrostatic attraction/hold between «lattice of» positive ions/cations AND delocalized «valence» electrons ✔

c.

Examiners report

Mostly well done which was a pleasant surprise since this is not overly easy, predictably some gave [Ar] 4s2 3d4.

a(i).

Despite some confusion regarding which sub-level the electrons were being removed from, many candidates were able to make at least one valid point, commonly in terms of lower energy/ full sub level/closer to nucleus.

a(ii).

This was an easy question, yet 30% of the candidates were unable to work it out; some wrote the oxidation state in the conventionally incorrect format, 1- and lost the mark.

b.

Most candidates knew the bonding in Fe is metallic but some did not “describe” it or missed the type of attraction, a minor mistake; others referred to nuclei or protons instead of cations/positive ions. In some cases, candidates referred too ionic bonding, probably still thinking of FeS2 (not reading the question well). Overall, only 30% answered satisfactorily.

c.

Syllabus sections

Core » Topic 4: Chemical bonding and structure » 4.5 Metallic bonding
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Core » Topic 4: Chemical bonding and structure
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