AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Students should be able to draw dot and cross diagrams for ionic compounds…
Full specification wording
Ionic bonding: Students should be able to draw dot and cross diagrams for ionic compounds formed by metals in Groups 1 and 2 with non-metals in Groups 6 and 7.
Ionic bonding joins a metal from Group 1 or 2 to a non-metal from Group 6 or 7.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 3 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Ionic bonding joins a metal from Group 1 or 2 to a non-metal from Group 6 or 7. Draw the outer shells only, using dots for one atom's electrons and crosses for the other's. A Group 1 atom loses its single outer electron to become a 1⁺ ion; a Group 2 atom loses two to become 2⁺. A Group 6 atom gains two electrons to become 2⁻; a Group 7 atom gains one to become 1⁻. Show the transfer with an arrow, then draw each ion with a full outer shell and square brackets carrying its charge. For sodium oxide, two Na atoms each give one electron to one O atom, giving 2Na⁺ and O²⁻. For magnesium chloride, one Mg atom gives one electron to each of two Cl atoms, giving Mg²⁺ and 2Cl⁻.
What earns the marks
- Outer-shell electrons only are shown; inner shells may be omitted or drawn as a labelled circle.
- Dots represent electrons from one atom and crosses those from the other, so the transfer is traceable.
- Group 1 and Group 2 metals lose one or two electrons respectively, forming 1⁺ and 2⁺ ions.
- Group 6 and Group 7 non-metals gain two or one electrons respectively, forming 2⁻ and 1⁻ ions.
- The number of metal and non-metal atoms drawn gives overall neutrality, for example two Na atoms per O atom in sodium oxide.
- Each ion is drawn with a complete outer shell and its charge shown, commonly in square brackets.
- An arrow or equivalent shows electron transfer from metal to non-metal.
- The diagram is labelled with the compound name or formula and the ion charges.
Common mistakes and how to put them right
Drawing full inner shells for every atom, which obscures the outer-shell transfer.
Put it right: Show only the outer shell or a labelled inner circle.
Giving a Group 2 metal a 1⁺ charge.
Put it right: Magnesium loses two electrons, so its ion is Mg²⁺.
Writing oxide as O²⁻ but then drawing only one sodium ion.
Put it right: Two Na⁺ ions are needed to balance one O²⁻.
Exam tips
- Count electrons before and after transfer to check each ion has a full outer shell.
- Check the total positive charge equals the total negative charge before finishing the diagram.
- Label charges clearly, for example Na⁺ and Cl⁻, rather than leaving the reader to infer them.
Try the lesson
The start of the Ionic bonding: Students should be able to draw dot and cross diagrams for ionic compounds formed by metals in Groups 1 and 2 with non-metals in Groups 6 and 7. lesson, made from checked teaching notes for this specification point.
Have a go first
Sodium is in Group 1 and chlorine is in Group 7. In a dot and cross diagram of sodium chloride, how many electrons are shown transferred from the sodium atom to the chlorine atom?
Listen
Ionic bonding joins a metal from Group 1 or 2 to a non-metal from Group 6 or 7. Draw the outer shells only, using dots for one atom's electrons and crosses for the other's. A Group 1 atom loses its single outer electron to become a 1⁺ ion; a Group 2 atom loses two to become 2⁺. A Group 6 atom gains two electrons to become 2⁻; a Group 7 atom gains one to become 1⁻. Show the transfer with an arrow, then draw each ion with a full outer shell and square brackets carrying its charge. For sodium oxide, two Na atoms each give one electron to one O atom, giving 2Na⁺ and O²⁻. For magnesium chloride, one Mg atom gives one electron to each of two Cl atoms, giving Mg²⁺ and 2Cl⁻. A strong answer earns marks for these points. Outer-shell electrons only are shown; inner shells may be omitted or drawn as a labelled circle. Dots represent electrons from one atom and crosses those from the other, so the transfer is traceable. Group 1 and Group 2 metals lose one or two electrons respectively, forming 1⁺ and 2⁺ ions. Group 6 and Group 7 non-metals gain two or one electrons respectively, forming 2⁻ and 1⁻ ions. Exam tip: Count electrons before and after transfer to check each ion has a full outer shell.
See it
Key words
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Electron transfer between metal and non-metal atoms
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Group number and ion charge
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Full outer shells and noble gas electron configurations
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Representing ions with dots, crosses and charges
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See every definition
- Electron transfer between metal and non-metal atoms
- An arrow or equivalent shows electron transfer from metal to non-metal, with dots for one atom's electrons and crosses for the other's.
- Group number and ion charge
- Group 1 and Group 2 metals lose one or two electrons respectively, forming 1⁺ and 2⁺ ions, while Group 6 and Group 7 non-metals gain two or one electrons respectively, forming 2⁻ and 1⁻ ions.
- Full outer shells and noble gas electron configurations
- Each ion is drawn with a complete outer shell, and electrons are counted before and after transfer to check each ion has a full outer shell.
- Representing ions with dots, crosses and charges
- Each ion is drawn with a complete outer shell and its charge shown, commonly in square brackets, labelled with the compound name or formula and the ion charges.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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Test your understanding of Ionic bonding: Students should be able to draw dot and cross diagrams for ionic compounds formed by metals in Groups 1 and 2 with non-metals in Groups 6 and 7.
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