O-LevelChemistryAtomic Structure5070/22 · May/June 2022 · Q48 Marks

The table shows information about some particles. | particle | number of protons | neutrons | electrons | |---|---|---|---| | 79Br 35 | 35 | 44 | 35 | | 79Br- 35 | 35 | 44 | | | 40Ca 20 | 20 | 20 | 20 | | 40Ca2+ 20 | 20 | 20 | 18 |

(a)State the nucleon number for 79Br/35.[1]
(b)State the number of electrons in 79Br-/35.[1]
(c)40Ca/20 is the full symbol for one isotope of calcium. Write the full symbol for one other isotope of calcium.[1]
(d)Describe how a calcium ion, Ca2+, is formed from a calcium atom, Ca.[1]
(e)(i)Calcium bromide is an ionic compound. Calcium bromide conducts electricity when molten but not when solid. Explain why calcium bromide conducts electricity when molten but not when solid.[2]
(e)(ii)Predict two other physical properties of calcium bromide. 1. 2.[2]

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[1] 79
[1] 36
[1] 41/20Ca
[1] loses two electrons
[1] in solid ions cannot move / in solid ions are in a lattice / in solid ions are fixed
[1] in molten liquid ions can move
[1] high melting point / high boiling point
[1] dissolves in water

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