DP Chemistry (last assessment 2024)

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Question 17N.2.hl.TZ0.3b

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Date November 2017 Marks available [Maximum mark: 3] Reference code 17N.2.hl.TZ0.3b
Level hl Paper 2 Time zone TZ0
Command term Explain Question number b Adapted from N/A
b.
[Maximum mark: 3]
17N.2.hl.TZ0.3b

Trends in physical and chemical properties are useful to chemists.

(b)

Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group whereas the melting points of the group 17 elements (F → I) increase down the group.

[3]

Markscheme

Any three of:

Group 1:
atomic/ionic radius increases

smaller charge density

OR

force of attraction between metal ions and delocalised electrons decreases

Do not accept discussion of attraction between valence electrons and nucleus for M2.

Accept “weaker metallic bonds” for M2.

Group 17:
number of electrons/surface area/molar mass increase

London/dispersion/van der Waals’/vdw forces increase

Accept “atomic mass” for “molar mass”.

[Max 3 Marks]

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