| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.sl.TZ1.6 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | 6 | Adapted from | N/A |
Question
Lanthanum, La, and antimony, Sb, form compounds with bromine that have similar formulas, LaBr3 and SbBr3.
Determine the type of bond present in SbBr3, showing your method. Use sections 8 and 29 of the data booklet.
[2]
a.
Lanthanum has a similar electronegativity to group 2 metals. Explain, in terms of bonding and structure, why crystalline lanthanum bromide is brittle.
[2]
b.
Markscheme
polar covalent
average electronegativity «= \(\frac{1}{2}\)(3.0 + 2.0)» = 2.5 AND electronegativity difference «= 3.0 – 2.0» = 1.0
[2 marks]
a.
ionic bonding
OR
electrostatic forces between ions
«slight» movement brings ions of same charge adjacent to each other «causing the crystal to break»
OR
«slight» movement results in repulsion between layers «causing the crystal to break»
[2 marks]
b.
Examiners report
[N/A]
a.
[N/A]
b.
