AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Non-metal atoms gain electrons to become negatively charged ions.
Full specification wording
Ionic bonding: Non-metal atoms gain electrons to become negatively charged ions.
Non-metal atoms have outer shells that are closer to full, so gaining electrons is energetically favourable and produces a negative ion.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Non-metal atoms have outer shells that are closer to full, so gaining electrons is energetically favourable and produces a negative ion. For example, a chlorine atom has the electronic structure 2,8,7; gaining one electron gives Cl⁻ with the structure 2,8,8, the same as argon. The number of electrons gained is usually 8 minus the group number for Groups 6 and 7, so oxygen (2,6) gains two electrons to form O²⁻ and chlorine gains one to form Cl⁻. The charge is written as a superscript after the symbol, and the size of the negative charge equals the number of electrons gained. This electron gain is the second half of ionic bonding and explains the anions in compounds such as NaCl and MgO.
What earns the marks
- Non-metal atoms gain electrons into their outermost shell until that shell is full.
- The number of electrons gained is 8 minus the group number for Groups 6 and 7.
- Gain of electrons produces a negative ion because the number of electrons now exceeds the number of protons.
- The charge on the ion is written as a superscript, for example O²⁻, F⁻ and Cl⁻.
- The electronic structure of the ion formed is that of the nearest noble gas, for example Cl⁻ is 2,8,8 like argon.
Common mistakes and how to put them right
Writing the charge on the baseline, such as Cl1⁻, instead of using a superscript.
Put it right: The correct form is Cl⁻.
Saying that non-metal atoms lose electrons to become negative ions.
Put it right: Non-metals gain electrons, and losing electrons would make the ion positive.
Miscounting the electrons gained, for example giving oxygen a single negative charge when it gains two electrons to form O²⁻.
Exam tips
- Count the electrons needed to complete the outer shell before writing the ion.
- Use the group number to work out the charge quickly: Group 7 forms 1⁻ ions and Group 6 forms 2⁻ ions.
- Check that the superscript charge is negative and matches the number of electrons gained.
Try the lesson
The start of the Ionic bonding: Non-metal atoms gain electrons to become negatively charged ions. lesson, made from checked teaching notes for this specification point.
Have a go first
A chlorine atom gains one electron when it forms an ion. What is the charge on the chloride ion?
Listen
Non-metal atoms have outer shells that are closer to full, so gaining electrons is energetically favourable and produces a negative ion. For example, a chlorine atom has the electronic structure 2,8,7; gaining one electron gives Cl⁻ with the structure 2,8,8, the same as argon. The number of electrons gained is usually 8 minus the group number for Groups 6 and 7, so oxygen (2,6) gains two electrons to form O²⁻ and chlorine gains one to form Cl⁻. The charge is written as a superscript after the symbol, and the size of the negative charge equals the number of electrons gained. This electron gain is the second half of ionic bonding and explains the anions in compounds such as NaCl and MgO. A strong answer earns marks for these points. Non-metal atoms gain electrons into their outermost shell until that shell is full. The number of electrons gained is 8 minus the group number for Groups 6 and 7. Gain of electrons produces a negative ion because the number of electrons now exceeds the number of protons. The charge on the ion is written as a superscript, for example O²⁻, F⁻ and Cl⁻. Exam tip: Count the electrons needed to complete the outer shell before writing the ion.
See it
Key words
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Ion formation by electron gain
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Charge and relative numbers of protons and electrons
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Representation of ions using symbols and superscripts
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Electronic structure and the periodic table
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See every definition
- Ion formation by electron gain
- Non-metal atoms gain electrons into their outermost shell until that shell is full, producing a negative ion.
- Charge and relative numbers of protons and electrons
- Gain of electrons produces a negative ion because the number of electrons now exceeds the number of protons.
- Representation of ions using symbols and superscripts
- The charge on the ion is written as a superscript after the symbol, for example O²⁻, F⁻ and Cl⁻.
- Electronic structure and the periodic table
- The electronic structure of the ion formed is that of the nearest noble gas, for example Cl⁻ is 2,8,8 like argon.
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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