Question Constellation Sign up for free AQA · GCSE · Chemistry · Higher
Forming calcium chloride ions
Calcium chloride is an ionic compound. Calcium and chlorine react to produce calcium chloride.
Describe what happens to calcium atoms and chlorine atoms when the ionic compound calcium chloride is formed.
Write your answer first. You can study the marking guidance whenever you need it.
Study the marking See what earns credit and compare it with a full-mark answer.
Marking points
- 1 States that each calcium atom loses two electrons.
- 2 States that each chlorine atom gains one electron.
- 3 Gives the 1 calcium atom : 2 chlorine atoms relationship.
- 4 Identifies formation of Ca²⁺ and Cl⁻ ions, or ions with full outer shells.
Full-mark answer
Each calcium atom transfers two electrons, losing both to form a Ca²⁺ ion. Two chlorine atoms each gain one electron to form two Cl⁻ ions, so one calcium atom reacts with two chlorine atoms and all the ions have full outer electron shells.
Why this answer loses marks
Calcium and chlorine share electrons.
Ionic formation transfers electrons; then the resulting charges and atom ratio must balance.