Predicting the properties of francium
3 marks · NormalExplain why francium compounds are expected to be colourless and soluble in water.
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Francium compounds are expected to be colourless and soluble in water because, like other alkali metal compounds, they do not have d-electrons to produce coloured ions, and their ionic compounds typically dissolve easily in water.
Must show: Does not form coloured ions, Alkali metal compounds dissolve in water
Also accept: No coloured ions are formed; Compounds dissolve due to their ionic nature and large ionic size
Common mistakes: Confusing colour of metal with colour of compounds
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Marking points
B1 · 1 mark · States that Group 1 compounds are colourless because they do not form coloured ions.
B2 · 1 mark · Mentions francium compounds are soluble in water because they are ionic/alkali metal compounds.
E1 · 1 mark · Relates francium's properties to the trends in alkali metals (trend justification).
Worked solution
Francium forms ionic compounds like the other alkali metals. These compounds do not have d-electrons to form coloured ions, so they are colourless. Alkali metal compounds are also typically soluble in water because their ions interact easily with water molecules.