Starter quiz
- Magnesium is in Group 2 of the periodic table. Which of the following statements about magnesium ions are correct?
- Magnesium atoms have two electrons in their outer shell. ✓
- Magnesium ions are more stable than magnesium atoms. ✓
- Magnesium ions have two electrons in their outer shell.
- Magnesium atoms can be represented by the symbol Mg²⁺.
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- Oxygen is a non-metal. What name is given to the type of ions that oxygen forms?
- 'anions' ✓
- Which of the following symbols represents a sodium ion?
- Na⁺ ✓
- Na²⁺
- Na⁻
- Na²⁻
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- True or false? Bromine atoms form stable Br⁻ ions.
- True ✓
- False
- Neon is found in Group 0 of the periodic table. Why is neon unreactive?
- Neon atoms do not need to lose or gain electrons to fill their outer shell. ✓
- Neon atoms are stable. ✓
- Neon atoms contain 0 electrons in their outer shell.
- Neon atoms have a full outer shell of electrons. ✓
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- An element has atoms containing 20 electrons. Which of the following statements about the element are true?
- The atoms of the element have 2 electrons in the outer shell. ✓
- The element forms ions with a charge of 2+. ✓
- The atoms of the element have 3 shells of electrons.
- The element forms ions with a charge of 2-.
- The atom is a metal. ✓
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Exit quiz
- Match the following terms to the correct definition.
- binary ionic substance⇔Made of two different elements, one a metal and one a non-metal. ✓
- magnitude⇔The size of a quantity. ✓
- dot-and-cross diagram⇔Used to show how chemical bonds are formed between atoms. ✓
- empirical formula⇔Simplest whole number ratio of atoms of each element in a compound. ✓
- Aluminium atoms ______ three electrons to form aluminium ions.
- 'lose' ✓
- Which of the following are binary ionic substances?
- NaCl, sodium chloride ✓
- CuCO₃, copper carbonate
- O₂, oxygen
- AlF₃, aluminium fluoride ✓
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This is a dot and cross diagram showing the bonding between sodium and chlorine. Which of the following statements about the image are correct.- The chlorine atom gained an electron to form an ion. ✓
- The sodium atom donated two electrons to the chloride ion.
- Both ions have a full outer shell of electrons. ✓
- The ratio of sodium to chloride ions in the substance is 2 : 1.
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- The formula for aluminium oxide is Al₂O₃. Which statements are correct?
- The ratio of aluminium ions to oxygen ions is 2 : 3. ✓
- The ratio of aluminium ions to oxygen ions is 3 : 2.
- The overall charge on aluminium oxide is neutral. ✓
- The charge on an aluminium is 3-.
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- Lithium ions, Li⁺ and oxygen ions, O²⁻, form lithium oxide. What is the empirical formula for lithium oxide?
- Li₂O ✓
- LiO₂
- Li₂O₂
- LiO
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- Dot and cross diagrams as a model for binary ionic substances
- Dot and cross diagrams show the empirical formula/ratio of atoms to show how electrons are transferred
- Ions are shown with full outer shells, square brackets, and a charge in the top right corner.
- Ionic compounds are neutral overall, so positive and negative charge must balance.
- When positive ions do not have the same magnitude of charge as negative ions, multiple of some ions will be required.
Common misconception
The ionic bond is the transfer of electrons and not the electrostatic forces of attraction between the ions. Dot and cross diagrams show the empirical formula of the lattice and not an ionic molecule.
Ensure students have a good understanding of how ions are formed, the arrangement of ions in a giant lattice structure and empricial formula before moving on to disucss using dot and cross diagrams to model ionic bonding.
Keywords
Binary ionic substance - is made up of two different elements, one of which is a metal and the other a non-metal element.
Empirical formula - show the simplest whole number ratio of atoms of each element in a compound.
Ratio - can be used to determine the size of one quantity in relation to another.
Dot-and-cross diagram - is used to show how chemical bonds are formed between atoms. The electrons from one atom are shown as dots and the electrons from the other atom are shown as crosses.
Magnitude - is the size of a quantity, for example the size of the charge on the ion.