Starter quiz
Below, there are six different models for representing the bonding and structure in the compound ethane. Match the image to the correct type of model.- a⇔dot-and-cross diagram ✓
- b⇔molecular formula ✓
- c⇔ball-and-stick model ✓
- d⇔empirical formula ✓
- e⇔displayed formula ✓
- f⇔space-filling model ✓
- What do the dots and crosses typically represent in dot-and-cross diagrams?
- 'electrons' ✓
- Which of the following are limitations of the empirical formula when representing molecules?
- it does not show the types of bonds ✓
- it does not indicate the actual number of atoms ✓
- it does not provide any spatial information ✓
- it serves as a step towards determining the molecular formula
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- Which model would not be appropriate to represent the bonding and/or structure in metals?
- ball-and-stick
- space-filling
- dot-and-cross ✓
- delocalised "sea" of electrons
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- What advantage does the ball-and-stick model have over the space-filling model?
- It shows the actual size of atoms more accurately.
- It clearly shows which atoms/ions have bonded. ✓
- It is easier to see the overall shape of the substance.
- It is more accurate in depicting electron sharing.
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- Which representation is most suitable for illustrating the arrangement of ions in a giant ionic lattice?
- molecular formula
- ball-and-stick model ✓
- displayed formula
- empirical formula
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Exit quiz
- Which properties of diamond are explained by the fact that each carbon atom is strongly bonded to four other carbon atoms in a rigid structure?
- electrical insulator
- high melting point ✓
- very hard ✓
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- What type of forces hold simple molecules together?
- covalent
- ionic
- intermolecular ✓
- metallic
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- One model of graphite shows it having free moving, delocalised electrons. This means graphite is an electrical ______?
- 'conductor' ✓
- Match each substance to the correct statement about it's structure and/or properties.
- diamond⇔doesn't conduct electricity as every atom is strongly bonded to others ✓
- graphite⇔hexagonal rings of carbon atoms, arranged in layers ✓
- carbon dioxide⇔made of simple molecules with low melting and boiling points ✓
- coal⇔a mixture of carbon-containing molecules ✓
- Match the key words to their definitions.
- simple molecular⇔distinct units made up of two or more atoms covalently bonded ✓
- model⇔represent parts of the natural world that are too difficult to observe ✓
- intermolecular force⇔weak forces of attraction between molecules ✓
- giant covalent⇔large regular arrangement of atoms all joined by covalent bonds ✓
- [a] covalent substances have [b] melting points as they're held together by strong covalent bonds. [c] covalent substances have [d] melting points as there are weak forces between molecules.
- giant, high, simple, low ✓
- giant, low, simple, high
- simple, high, giant, low
- simple, low, giant, high
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Worksheet
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Lesson Details
Key learning points
- Molecular modelling represents the bonding and structure of substances.
- The way giant covalent structures melt/boil is very different to simple molecules.
- Diamond is very hard, has a very high melting point and does not conduct electricity, every atom is bonded to another.
- In graphite each atom is bonded to three others to form layers of hexagonal rings. Each atom contributes a free electron
- Simple molecules are held together by intermolecular forces, no chemical bonds hold them together.
Common misconception
Covalent bonds break in simple molecules for substances to melt/boil, because this happens in giant covalent structures.
Highlight that bonds require large amounts of energy to break, hence the very high melting points of diamond and graphite. As all atoms are bonded these must be broken to melt/boil.
Keywords
Simple molecular - Simple molecular substances are made up of two or more atoms covalently bonded together to form a distinct unit.
Model - Scientists use models to represent parts of the natural world that are too difficult to observe or explain directly.
Intermolecular force - Intermolecular forces are weak forces of attraction between molecules and molecular substances.
Giant covalent - A giant covalent substance has a large regular arrangement of atoms all joined together by covalent bonds.
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