AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
This means that most metals have high melting and boiling points.
Full specification wording
Properties of metals and alloys: This means that most metals have high melting and boiling points.
Melting and boiling require energy to overcome the forces holding particles together.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Melting and boiling require energy to overcome the forces holding particles together. In a metal, the particles are positive ions held by strong metallic bonds to a sea of delocalised electrons. Because these bonds act throughout a giant lattice, a large amount of energy is needed to break them. This is why most metals have high melting and boiling points. For example, magnesium melts at about 650 °C and iron at about 1538 °C, both much higher than the melting point of a simple molecular substance such as iodine. The stronger the metallic bonding and the more electrons donated per atom, the higher the melting point tends to be. Metals with weaker metallic bonding, such as mercury, are liquid at room temperature.
What earns the marks
- Melting and boiling involve overcoming the strong metallic bonds between positive metal ions and delocalised electrons.
- The giant lattice means many strong bonds must be broken, so a large amount of energy is required.
- Most metals therefore have high melting and boiling points compared with simple molecular substances.
- The strength of metallic bonding varies between metals, so melting points vary; for example, mercury is liquid at room temperature while iron has a very high melting point.
- A valid comparison, such as magnesium melting at about 650 °C versus iodine melting at about 114 °C, supports the explanation.
Common mistakes and how to put them right
Saying that melting breaks covalent bonds inside metal molecules.
Put it right: Metallic bonds between ions and delocalised electrons are overcome.
Claiming that all metals have equally high melting points.
Put it right: The strength of metallic bonding differs, so values range widely.
Stating that melting point depends on the number of delocalised electrons only.
Put it right: Ion charge, ion size and lattice arrangement also affect bond strength.
Exam tips
- Always name the force being overcome when explaining a melting or boiling point.
- Use a comparison with a simple molecular substance to make the high value meaningful.
- If a data table is given, quote a specific melting point to support your explanation rather than saying it is high.
Try the lesson
The start of the Properties of metals and alloys: This means that most metals have high melting and boiling points. lesson, made from checked teaching notes for this specification point.
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Why do most metals have high melting points?
Listen
Melting and boiling require energy to overcome the forces holding particles together. In a metal, the particles are positive ions held by strong metallic bonds to a sea of delocalised electrons. Because these bonds act throughout a giant lattice, a large amount of energy is needed to break them. This is why most metals have high melting and boiling points. For example, magnesium melts at about 650 °C and iron at about 1538 °C, both much higher than the melting point of a simple molecular substance such as iodine. The stronger the metallic bonding and the more electrons donated per atom, the higher the melting point tends to be. Metals with weaker metallic bonding, such as mercury, are liquid at room temperature. A strong answer earns marks for these points. Melting and boiling involve overcoming the strong metallic bonds between positive metal ions and delocalised electrons. The giant lattice means many strong bonds must be broken, so a large amount of energy is required. Most metals therefore have high melting and boiling points compared with simple molecular substances. The strength of metallic bonding varies between metals, so melting points vary; for example, mercury is liquid at room temperature while iron has a very high melting point. A common slip: Saying that melting breaks covalent bonds inside metal molecules. Instead, metallic bonds between ions and delocalised electrons are overcome. Exam tip: Always name the force being overcome when explaining a melting or boiling point.
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Key words
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Metallic bonds
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Giant lattice
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Melting and boiling
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Strength of metallic bonding
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See every definition
- Metallic bonds
- Strong bonds that hold positive ions to a sea of delocalised electrons in a metal.
- Giant lattice
- A structure in which the bonds act throughout, so a large amount of energy is needed to break them.
- Melting and boiling
- Changes that require energy to overcome the forces holding particles together.
- Strength of metallic bonding
- This varies between metals, so melting points vary, and the more electrons donated per atom, the higher the melting point tends to be.
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