AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
The electron transfer during the formation of an ionic compound can be…
Full specification wording
Ionic bonding: The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram, eg for sodium chloride 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.
A dot and cross diagram shows how electrons are transferred when an ionic compound forms.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 5 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A dot and cross diagram shows how electrons are transferred when an ionic compound forms. For sodium chloride, draw the sodium atom with its outer electron as a dot and the chlorine atom with seven outer electrons as crosses. Move the dot from sodium to chlorine so that chlorine now has eight outer electrons, shown as seven crosses and one dot. Then draw the ions in square brackets with the charges outside: Na⁺ and Cl⁻. For magnesium oxide, magnesium loses two electrons to oxygen, so two dots move to oxygen and the ions are Mg²⁺ and O²⁻. The diagram must show full outer shells on both ions, correct charges, and square brackets around each ion. This method works for Group 1 and 2 metals with Group 6 and 7 non-metals.
What earns the marks
- Draw the outer shell electrons of each atom using dots for one atom and crosses for the other.
- Show the transfer of electrons from the metal atom to the non-metal atom.
- Draw square brackets around each ion and write the charge outside the bracket.
- Ensure each ion has a full outer shell of eight electrons, except for small ions such as Li⁺ which have two.
- Use the correct number of electrons transferred, for example two for MgO and one for NaCl.
Common mistakes and how to put them right
Drawing the ions without square brackets or charges, which fails to show that ions have formed.
Showing the wrong number of electrons transferred, for example moving one electron from magnesium instead of two.
Leaving the outer shell of an ion incomplete, for example showing Cl⁻ with seven outer electrons instead of eight.
Exam tips
- Use dots for one element and crosses for the other so the transfer is easy to see.
- Check the charge on each ion matches the number of electrons lost or gained.
- Include square brackets and charges for every ion in the final diagram.
Try the lesson
The start of the Ionic bonding: The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram, eg for sodium chloride 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
In a dot and cross diagram for sodium chloride, what does each dot or cross represent?
Listen
A dot and cross diagram shows how electrons are transferred when an ionic compound forms. For sodium chloride, draw the sodium atom with its outer electron as a dot and the chlorine atom with seven outer electrons as crosses. Move the dot from sodium to chlorine so that chlorine now has eight outer electrons, shown as seven crosses and one dot. Then draw the ions in square brackets with the charges outside: Na⁺ and Cl⁻. For magnesium oxide, magnesium loses two electrons to oxygen, so two dots move to oxygen and the ions are Mg²⁺ and O²⁻. The diagram must show full outer shells on both ions, correct charges, and square brackets around each ion. This method works for Group 1 and 2 metals with Group 6 and 7 non-metals. A strong answer earns marks for these points. Draw the outer shell electrons of each atom using dots for one atom and crosses for the other. Show the transfer of electrons from the metal atom to the non-metal atom. Draw square brackets around each ion and write the charge outside the bracket. Ensure each ion has a full outer shell of eight electrons, except for small ions such as Li⁺ which have two. Exam tip: Use dots for one element and crosses for the other so the transfer is easy to see.
See it
Put it in order
Put these steps in the order they happen.
- 1. Transfer the dot from sodium to chlorine
- 2. Chlorine atom: seven outer electrons shown as crosses
- 3. Sodium atom: outer electron shown as a dot
- 4. Check full outer shells and correct charges
- 5. Draw ions in square brackets with charges outside: Na⁺ and Cl⁻
- 6. Chlorine now has eight outer electrons: seven crosses and one dot
Key words
Say what each word means before you turn the card.
dot and cross diagram
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electron transfer
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square brackets
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full outer shell
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See every definition
- dot and cross diagram
- A diagram that represents the electron transfer during the formation of an ionic compound, using dots for one atom and crosses for the other.
- electron transfer
- The movement of electrons from the metal atom to the non-metal atom when an ionic compound forms.
- square brackets
- Drawn around each ion in the final diagram, with the charge written outside the bracket.
- full outer shell
- Each ion has eight electrons in its outer shell, except for small ions such as Li⁺ which have two.
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: The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram, eg for sodium chloride 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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