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Date	May 2019	Marks available	2	Reference code	19M.3.hl.TZ1.1
Level	HL	Paper	3	Time zone	TZ1
Command term	Deduce	Question number	1	Adapted from	N/A

Question

Physical properties of elements vary according to atomic number. Sections 6 to 9 of the data
booklet list some of these properties.

Melting points and boiling points of elements 1 to 95

Deduce, giving a reason, the group of elements in the periodic table most likely to undergo sublimation.

[2]

Describe the density trend across periods 4 and 5 of the periodic table.

[1]

b(i).

Suggest, with a reason, whether the lanthanoids or actinoids of the f-block would have the higher density.

[1]

b(ii).

Compare the ease of oxidation of s-block and d-block metals to their melting points and densities. Use section 25 of the data booklet.

[2]

b(iii).

Sketch how the first ionization energies of elements vary with their atomic radius.

[1]

b(iv).

Markscheme

group 18/noble gases [✔]

smallest difference between melting and boiling points
OR
weakest intermolecular forces «in that period» [✔]

Note: Accept “group 17/halogens”.

density increases «to a maximum in the transition elements» AND then decreases [✔]

b(i).

actinoids AND density increases down all groups «due to large increase in atomic mass for small increase in atomic volume»
OR
actinoids AND «much» greater atomic mass with similar type of bonding
OR
actinoids AND density «of actinoids» atomic number 90 to 95 is greater than corresponding lanthanoids [✔]

Note: Accept “actinoids AND on graph actinoids have «much» greater density than lanthanoids”.

b(ii).

Alternative 1:
«metals with» low densities oxidize easier [✔]

«metals with» low melting points oxidize easier [✔]

Alternative 2:
in s-block «metals with» high densities oxidize easier
OR
in s-block «metals with» low melting points oxidize easier [✔]

in d-block «metals with» low densities oxidize easier
OR
in d-block «metals with» low melting points oxidize easier [✔]

Note: Award [1 max] for “s-block metals more easily oxidized” OR “s-block metals have lower melting points” OR “s-block metals have lower densities”.

Accept “have greater activity” for “oxidize easier”.

b(iii).

[✔]

Note: Accept any negative sloping line.

Do not award mark if line touches either axis.

b(iv).

Examiners report

Most candidates correctly identified the group of elements most likely to undergo sublimation but did not score for the reason as they referred to low melting and boiling points, rather than the smallest difference between these temperatures. There were several G2 comments that “the group of elements” was a confusing requirement as elements could be grouped in many ways, including for instance, from B to Ne. The Chemistry Guide clearly states that a group on the periodic table refers to a vertical column of elements. A few complaints were received about the inclusion of a question on sublimation, but the question was designed to make candidates think, and did not require knowledge of phase diagrams.

Required candidates to consider density trends. Most candidates correctly described trends across periods 4 and 5 but had difficulty predicting and explaining whether lanthanoids or actinoids would have the higher density. Many said that actinoids would have higher density because they have more protons and neutrons / greater atomic number / greater mass with no further detail about having similar bonding and hence similar volume. Some G2 comments complained about the inclusion of lanthanoids and actinoids in this question. However, the Chemistry Guide clearly states that these terms should be known.

b(i).

[N/A]

b(ii).

Most candidates scored at least 1 mark for comparing the s-block and d-block metals and most drew a line with a negative slope.

b(iii).

Although many here failed to score because the line crossed or touched one of the axes. A few sketched a graph reminiscent of first ionization energy against atomic number.

b(iv).

Syllabus sections

Core » Topic 1: Stoichiometric relationships » 1.1 Introduction to the particulate nature of matter and chemical change

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