Representing Ionic Bonds
Applied Science: BTEC Level 3 National Extended Diploma, topic 1.1.4
Dot-and-Cross Diagrams
Dot-and-cross diagrams can show electrons being transferred and ions being formed. Dots represent electrons from 1 atom and crosses represent electrons from the other atom. Square brackets and a charge (e.g. 2+) represent ions.
How is sodium fluoride formed?
- The sodium atom transfers its outer electron to the fluorine atom, creating Na+ and F- ions. Both of these ions have full outer shells.
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How is calcium oxide formed?
- The calcium atom transfers its 2 outer electrons to the oxygen atom, creating Ca2+ and O2- ions which both have full outer shells.
Empirical Formulae
You can work out the proportion of each ion in a compound. The empirical formula of an ionic compound is the simplest ratio of ions possible.
Ca2+ and F-
- In order for the charges to balance out and for the overall formula to be neutral, there must be 2 F- ions for each Ca2+ ion.
- The empirical formula is CaF2
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Na+ + SO42-
- In order for the charges to balance out and for the overall formula to be neutral, there must be 2 Na+ ions for each SO42- ion.
- The empirical formula is Na2SO4.
Test yourself on Representing Ionic Bonds
What can we show using dot-and-cross diagrams?
Sodium is in group 1 and oxygen is in group 6. In the dot-and-cross diagram for sodium oxide, how many sodium ions would there be?
What do we call the electrostatic forces that hold ionic lattices together?
What type of structure are ionic lattices?
Which of the following is true about ionic lattices?