DP Chemistry (last assessment 2024)

Question 18N.3.hl.TZ0.2a

Date	November 2018	Marks available	[Maximum mark: 2]	Reference code	18N.3.hl.TZ0.2a
Level	hl	Paper	3	Time zone	TZ0
Command term	Outline	Question number	a	Adapted from	N/A

[Maximum mark: 2]

18N.3.hl.TZ0.2a

One way of classifying materials is based on the type of bonding present.

(a)

Outline why this type of classification is not entirely satisfactory by using magnesium diboride, MgB₂, as an example. Refer to sections 8 and 29 of the data booklet.

[2]

Markscheme

$\Delta \chi$ = 0.7 AND average $\Delta \chi$ = 1.7 ✔

bonding between metallic and ionic

more than one type of bonding present

bond type difficult to determine as close to several regions/several types/named bonding types «eg ionic and covalent etc.»

bond is mostly covalent «based on % covalent scale on diagram»

bond has « $\frac{{0.7}}{{3.2}} \times 100 =$ » 22% ionic character ✔

Accept “EN” for “ $\chi$ ".

Accept “bond is ionic but close to several regions/several types/other named bonding type(s) (eg covalent, metallic and covalent etc.)”.

Do not accept just “bond is ionic”.

Accept any value for % ionic character in range 15–24% or % covalent character in range 76–85%.