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4.6Chemistry 01. Materials And Their Structure

Ions are atoms that have gained or lost electrons to become charged — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions

5 min read 6 parts Lesson 6 of 11 1 quiz

📚 Cambridge Checkpoint Science 0893 Hub / Topical Revision
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Lesson summary

4.6 Ions: atoms that have gained or lost electrons — CHECKPOINT - Lower Secondary Science 0893 notes: Describe how atoms become positive or negative ions by losing or gaining electrons and write the symbols and charges of ions.Stable atoms — atoms are more stable when the outermo…

  • Noble gases
  • Other elements
  • Metal atoms
  • Positive ion
  • Electrostatic force
  • Stable atoms — atoms are more stable when the outermost electron shell is full

Section 1 of 6Why atoms form ions

  • Stable atoms
    • atoms are more stable when the outermost electron shell is full.
  • Noble gases
    • the Group 8 elements already have full outer shells, so they do not react to form compounds.
  • Other elements
    • they gain, lose or share electrons to fill their outer shells.

Section 2 of 6Ion

  • Ion
    • an atom that has gained or lost electrons and so has become charged.
    • Protons have a charge of +1 and electrons have a charge of -1.
    • An atom has no overall charge because its protons and electrons are equal in number.

Section 3 of 6Positive ions by losing electrons

  • Metal atoms
    • they lose electrons from the outermost shell to form positive ions.
  • Sodium
    • a sodium atom [2,8,1] loses one electron and becomes a sodium ion Na+ [2,8].
    • It has 11 protons and 10 electrons, so it has an overall charge of +1.
    • The next shell is now the outermost shell and it is full.

Section 4 of 6Negative ions by gaining electrons

  • Non-metal atoms
    • they gain electrons to fill the outermost shell and form negative ions.
  • Chlorine
    • a chlorine atom [2,8,7] gains one electron and becomes a chloride ion Cl- [2,8,8].
    • It has 17 protons and 18 electrons, so it has an overall charge of -1.

Section 5 of 6Ions with a larger charge

AtomElectrons movedIon
Magnesium [2,8,2]Loses 2Mg2+ [2,8]
Oxygen [2,6]Gains 2O2- [2,8]
Lithium [2,1]Loses 1Li+ [2]
Fluorine [2,7]Gains 1F- [2,8]

Section 6 of 6Reactivity and ion formation

1Group 12 points
  • potassium is the most reactive and lithium the least reactive.
  • Potassium's outer electron is furthest from the protons, so the electrostatic force is weaker and it is lost more easily.
2Group 72 points
  • fluorine is more reactive than chlorine.
  • Fluorine's outer shell is closer to the protons, so it attracts an extra electron more strongly.

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