Question Constellation Sign up for free AQA · GCSE · Chemistry · Higher
Forming calcium chloride ions
Halogens are elements in Group 7 of the periodic table.
Calcium reacts with chlorine to produce calcium chloride.
Explain what happens to calcium atoms and to chlorine atoms when calcium reacts with chlorine to produce calcium chloride.
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Marking points
- 1 States that each calcium atom loses two electrons.
- 2 States that each chlorine atom gains one electron.
- 3 Relates one calcium atom to two chlorine atoms.
- 4 Identifies the Ca²⁺ and Cl⁻ ions formed, or their full outer shells.
Full-mark answer
Each calcium atom loses two electrons. Each chlorine atom gains one electron, so one calcium atom transfers electrons to two chlorine atoms. This forms Ca²⁺ ions and Cl⁻ ions with full outer shells.
Why this answer loses marks
Calcium and chlorine share electrons to form molecules.
This is ionic formation, so calcium loses electrons, chlorine gains them, and the reacting ratio and ion charges must balance.