AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Atoms turn into positive ions if they lose one or more outer electron(s).
Full specification wording
Mass number, atomic number and isotopes: Atoms turn into positive ions if they lose one or more outer electron(s).
A neutral atom has equal numbers of protons and electrons.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 6 of 7
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A neutral atom has equal numbers of protons and electrons. The outer electrons are the ones most easily removed because they are furthest from the nucleus and least strongly attracted. When an atom loses one or more of these outer electrons, the number of protons exceeds the number of electrons, so the overall charge becomes positive and the particle is a positive ion. For example, a sodium atom has 11 protons and 11 electrons; losing one outer electron leaves 11 protons and 10 electrons, giving a 1⁺ charge and the ion Na⁺. The nucleus is unchanged, so the proton number and the element identity stay the same; only the electron count and charge change.
What earns the marks
- State that a neutral atom has equal numbers of protons and electrons.
- State that losing electrons leaves more protons than electrons, producing an overall positive charge.
- Identify the electrons lost as outer electrons, and link this to their weaker attraction to the nucleus.
- Work out the charge from the numbers of protons and electrons, for example 11 protons and 10 electrons gives a 1⁺ charge.
- Write the ion symbol correctly, such as Na⁺ or Mg²⁺, showing the charge as a superscript.
- Recognise that the nucleus and proton number do not change when an atom forms a positive ion.
Common mistakes and how to put them right
Saying that atoms become positive ions by gaining protons.
Put it right by stating that protons are fixed in the nucleus and it is the loss of electrons that creates the positive charge.
Writing the charge after the symbol on the baseline, such as Na+.
Put it right by writing the charge as a superscript, Na⁺.
Thinking that any electron can be lost equally easily.
Put it right by explaining that outer electrons are lost first because they are furthest from the nucleus and least strongly attracted.
Exam tips
- Count protons and electrons separately before deciding the charge, then compare the two totals.
- Use the group number of a main-group element to predict the charge of its ion, for example Group 1 gives 1⁺ and Group 2 gives 2⁺.
- Check that the number of electrons lost matches the size of the positive charge, so the two parts of the answer agree.
Try the lesson
The start of the Mass number, atomic number and isotopes: Atoms turn into positive ions if they lose one or more outer electron(s). lesson, made from checked teaching notes for this specification point.
Have a go first
A sodium atom loses one outer electron. What charge does the sodium ion formed have?
Listen
A neutral atom has equal numbers of protons and electrons. The outer electrons are the ones most easily removed because they are furthest from the nucleus and least strongly attracted. When an atom loses one or more of these outer electrons, the number of protons exceeds the number of electrons, so the overall charge becomes positive and the particle is a positive ion. For example, a sodium atom has 11 protons and 11 electrons; losing one outer electron leaves 11 protons and 10 electrons, giving a 1⁺ charge and the ion Na⁺. The nucleus is unchanged, so the proton number and the element identity stay the same; only the electron count and charge change. A strong answer earns marks for these points. State that a neutral atom has equal numbers of protons and electrons. State that losing electrons leaves more protons than electrons, producing an overall positive charge. Identify the electrons lost as outer electrons, and link this to their weaker attraction to the nucleus. Work out the charge from the numbers of protons and electrons, for example 11 protons and 10 electrons gives a 1⁺ charge. A common slip: Saying that atoms become positive ions by gaining protons. Instead, stating that protons are fixed in the nucleus and it is the loss of electrons that creates the positive charge. Exam tip: Count protons and electrons separately before deciding the charge, then compare the two totals.
Key words
Say what each word means before you turn the card.
Ion formation
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Electron arrangement and outer electrons
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Protons, neutrons and electrons
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See every definition
- Ion formation
- Atoms turn into positive ions if they lose one or more outer electron(s), so the number of protons exceeds the number of electrons and the overall charge becomes positive.
- Electron arrangement and outer electrons
- The outer electrons are the ones most easily removed because they are furthest from the nucleus and least strongly attracted.
- Protons, neutrons and electrons
- A neutral atom has equal numbers of protons and electrons, and losing electrons leaves more protons than electrons, producing an overall positive charge.
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