AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Students should be able to work out the charge on the ions of metals and…
Full specification wording
Ionic bonding: Students should be able to work out the charge on the ions of metals and non-metals from the group number of the element, limited to the metals in Groups 1 and 2, and non-metals in Groups 6 and 7.
Atoms in Groups 1 and 2 lose their outer-shell electrons to form positive ions, while atoms in Groups 6 and 7 gain electrons to complete their outer shell and form negative ions.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 5 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Atoms in Groups 1 and 2 lose their outer-shell electrons to form positive ions, while atoms in Groups 6 and 7 gain electrons to complete their outer shell and form negative ions. The group number tells you how many outer electrons a metal loses, whereas for non-metals, 8 minus the group number gives the number of electrons gained. For example, sodium (Group 1) loses one electron to form Na⁺, magnesium (Group 2) loses two to form Mg²⁺, oxygen (Group 6) gains two to form O²⁻, and chlorine (Group 7) gains one to form Cl⁻. The size of the charge equals the number of electrons transferred, and the sign shows whether electrons were lost or gained. This lets you predict ion charges directly from the periodic table.
What earns the marks
- Group 1 metals lose one outer electron and form ions with a 1+ charge, such as Na⁺ and K⁺.
- Group 2 metals lose two outer electrons and form ions with a 2+ charge, such as Mg²⁺ and Ca²⁺.
- Group 6 non-metals gain two electrons and form ions with a 2- charge, such as O²⁻ and S²⁻.
- Group 7 non-metals gain one electron and form ions with a 1- charge, such as Cl⁻ and Br⁻.
- The number of electrons lost or gained equals the size of the charge, and the sign shows loss (positive) or gain (negative).
- Ion charges can be deduced from group number alone for these groups, without writing full electron configurations.
Common mistakes and how to put them right
Writing the charge after the symbol as a plain number, for example Na1.
Put it right: The correct notation places the charge as a superscript, Na⁺.
Giving Group 6 non-metals a 6- charge by copying the group number.
Put it right: The correct charge is 2- because they gain two electrons (8 minus 6).
Assuming all metals form 1+ ions.
Put it right: Group 2 metals such as magnesium form 2+ ions because they lose two electrons.
Exam tips
- Link each group number to a fixed electron change: Group 1 loses 1, Group 2 loses 2, Group 6 gains 2, Group 7 gains 1.
- Check the sign first, then the size of the charge, then write it as a superscript on the symbol.
- Practise with unfamiliar elements in the same groups, such as potassium, calcium, sulfur and bromine, to show the pattern is general.
Try the lesson
The start of the Ionic bonding: Students should be able to work out the charge on the ions of metals and non-metals from the group number of the element, limited to the metals in Groups 1 and 2, and non-metals in Groups 6 and 7. lesson, made from checked teaching notes for this specification point.
Have a go first
Potassium is a metal in Group 1. What is the charge on the ion that potassium forms?
Listen
Atoms in Groups 1 and 2 lose their outer-shell electrons to form positive ions, while atoms in Groups 6 and 7 gain electrons to complete their outer shell and form negative ions. The group number tells you how many outer electrons a metal loses, whereas for non-metals, 8 minus the group number gives the number of electrons gained. For example, sodium (Group 1) loses one electron to form Na⁺, magnesium (Group 2) loses two to form Mg²⁺, oxygen (Group 6) gains two to form O²⁻, and chlorine (Group 7) gains one to form Cl⁻. The size of the charge equals the number of electrons transferred, and the sign shows whether electrons were lost or gained. This lets you predict ion charges directly from the periodic table. A strong answer earns marks for these points. Group 1 metals lose one outer electron and form ions with a 1+ charge, such as Na⁺ and K⁺. Group 2 metals lose two outer electrons and form ions with a 2+ charge, such as Mg²⁺ and Ca²⁺. Group 6 non-metals gain two electrons and form ions with a 2- charge, such as O²⁻ and S²⁻. Group 7 non-metals gain one electron and form ions with a 1- charge, such as Cl⁻ and Br⁻. Exam tip: Link each group number to a fixed electron change: Group 1 loses 1, Group 2 loses 2, Group 6 gains 2, Group 7 gains 1.
See it
Key words
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Periodic table patterns
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Electron transfer and ion formation
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Charge and notation
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Predicting ion charges from group number
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See every definition
- Periodic table patterns
- The group number tells you how many outer electrons a metal loses, whereas for non-metals, 8 minus the group number gives the number of electrons gained.
- Electron transfer and ion formation
- Atoms in Groups 1 and 2 lose their outer-shell electrons to form positive ions, while atoms in Groups 6 and 7 gain electrons to complete their outer shell and form negative ions.
- Charge and notation
- The size of the charge equals the number of electrons transferred, and the sign shows whether electrons were lost or gained, written as a superscript on the symbol.
- Predicting ion charges from group number
- Ion charges can be deduced from group number alone for these groups, without writing full electron configurations.
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 work out the charge on the ions of metals and non-metals from the group number of the element, limited to the metals in Groups 1 and 2, and non-metals in Groups 6 and 7.
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