AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Ionic bonding: Metal atoms lose electrons to become positively charged ions.
Metal atoms have relatively few electrons in their outer shell, so losing those electrons is energetically favourable and produces a positive ion.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 7
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Metal atoms have relatively few electrons in their outer shell, so losing those electrons is energetically favourable and produces a positive ion. For example, a sodium atom has the electronic structure 2,8,1; losing its single outer electron gives Na⁺ with the structure 2,8, which is the same as neon. The number of electrons lost equals the group number for Groups 1, 2 and 3, so magnesium (2,8,2) loses two electrons to form Mg²⁺. The charge is written as a superscript after the symbol, and the size of the charge matches the number of electrons lost. This electron loss is the first half of ionic bonding and explains why metals form cations in compounds such as NaCl and MgO.
What earns the marks
- Metal atoms lose the electrons in their outermost shell first, because these are the least strongly attracted to the nucleus.
- The number of electrons lost by a metal atom is equal to its group number for Groups 1, 2 and 3.
- Loss of electrons produces a positive ion because the number of protons now exceeds the number of electrons.
- The charge on the ion is written as a superscript, for example Na⁺, Mg²⁺ and Al³⁺.
- The electronic structure of the ion formed is that of the nearest noble gas, for example Na⁺ is 2,8 like neon.
Common mistakes and how to put them right
Writing the charge after the symbol on the baseline, such as Na1⁺, instead of using a superscript.
Put it right: The correct form is Na⁺.
Saying that metal atoms gain electrons to become positive ions.
Put it right: Metals lose electrons, and gaining electrons would make the ion negative.
Forgetting to balance the charge with the number of electrons lost, for example writing Mg⁺ when magnesium loses two electrons and forms Mg²⁺.
Exam tips
- State clearly that electrons are lost from the outer shell, not from the nucleus.
- Link the group number to the number of electrons lost before writing the ion symbol.
- Check that the superscript charge matches the number of electrons removed, and that the sign is positive.
Try the lesson
The start of the Ionic bonding: Metal atoms lose electrons to become positively charged ions. lesson, made from checked teaching notes for this specification point.
Have a go first
A magnesium atom loses two electrons when it forms an ion. What is the charge on the magnesium ion formed?
Listen
Metal atoms have relatively few electrons in their outer shell, so losing those electrons is energetically favourable and produces a positive ion. For example, a sodium atom has the electronic structure 2,8,1; losing its single outer electron gives Na⁺ with the structure 2,8, which is the same as neon. The number of electrons lost equals the group number for Groups 1, 2 and 3, so magnesium (2,8,2) loses two electrons to form Mg²⁺. The charge is written as a superscript after the symbol, and the size of the charge matches the number of electrons lost. This electron loss is the first half of ionic bonding and explains why metals form cations in compounds such as NaCl and MgO. A strong answer earns marks for these points. Metal atoms lose the electrons in their outermost shell first, because these are the least strongly attracted to the nucleus. The number of electrons lost by a metal atom is equal to its group number for Groups 1, 2 and 3. Loss of electrons produces a positive ion because the number of protons now exceeds the number of electrons. The charge on the ion is written as a superscript, for example Na⁺, Mg²⁺ and Al³⁺. Exam tip: State clearly that electrons are lost from the outer shell, not from the nucleus.
See it
Key words
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Ion formation by electron loss
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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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See every definition
- Ion formation by electron loss
- Metal atoms lose electrons to become positively charged ions, losing the electrons in their outermost shell first because these are the least strongly attracted to the nucleus.
- Charge and relative numbers of protons and electrons
- Loss of electrons produces a positive ion because the number of protons now exceeds the number of electrons, and the size of the charge matches the number of electrons lost.
- Representation of ions using symbols and superscripts
- The charge on the ion is written as a superscript after the symbol, and the superscript charge must match the number of electrons removed, with a positive sign.
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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