Giant Structures (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Chemistry): Flashcards

Exam code: 0654 & 0973

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  • Describe the bonding arrangement of carbon atoms in diamond.

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  • Describe the bonding arrangement of carbon atoms in diamond.

    In diamond, each carbon atom forms covalent bonds with four other carbon atoms in a tetrahedral arrangement. All electrons are held in covalent bonds, leaving no free electrons.

  • True or False?

    Diamond and graphite are allotropes of carbon, meaning they contain only carbon atoms but have different structures.

    True.

    Diamond and graphite are both allotropes of carbon: they both consist only of carbon atoms, but their different bonding arrangements give them completely different physical properties.

  • In graphite, each carbon atom bonds to ______ others, leaving ______ delocalised electron per atom, which allows graphite to ______ electricity.

    In graphite, each carbon atom bonds to 3 others, leaving 1 delocalised electron per atom, which allows graphite to conduct electricity.

  • Why does diamond not conduct electricity but graphite does?

    In diamond, all four outer electrons of each carbon atom are used in covalent bonds, leaving no free electrons to carry a charge.

    In graphite, each carbon uses only three electrons for bonding, leaving one delocalised electron per atom that can move through the structure and carry a charge.

  • True or False?

    Graphite is slippery because the covalent bonds between carbon atoms within each layer are weak.

    False.

    The covalent bonds within each graphite layer are strong. Graphite is slippery because the forces between the layers are weak intermolecular forces, allowing the layers to slide over each other easily.

  • Why do both diamond and graphite have very high melting points?

    Both diamond and graphite have giant covalent structures. A very large amount of energy is needed to break the many strong covalent bonds between carbon atoms throughout the structure, giving both substances very high melting points.

  • Diamond is ______ and does not conduct electricity because each carbon atom bonds to ______ others using all its outer electrons, leaving ______ free electrons.

    Diamond is hard and does not conduct electricity because each carbon atom bonds to 4 others using all its outer electrons, leaving no free electrons.

  • What is a metallic bond?

    A metallic bond is the strong electrostatic force of attraction between a lattice of positive metal ions and the surrounding delocalised electrons. The delocalised electrons are free to move between the ions throughout the structure.

  • True or False?

    In a metal, atoms lose their outer electrons to become positive ions, while those electrons become delocalised and move freely through the lattice.

    True.

    Metal atoms lose their outer electrons to become positive ions. These electrons are no longer associated with any particular atom and are delocalised, forming a sea of electrons that holds the lattice together.

  • Metals conduct electricity because the ______ electrons are free to ______ through the structure and carry a ______.

    Metals conduct electricity because the delocalised electrons are free to move through the structure and carry a charge.

  • Why do metals have high melting points?

    Metals have a giant structure with strong electrostatic forces of attraction between the positive metal ions and the delocalised electrons throughout the lattice. A large amount of energy is needed to overcome these forces.

  • True or False?

    Metals are malleable because the layers of positive ions can slide over each other without breaking the metallic bonds.

    True.

    The layers of positive ions in a metal can slide over each other when a force is applied. The delocalised electrons move to maintain the attraction throughout the structure, so the metal can be reshaped without shattering.

  • Why do metals conduct electricity but ionic compounds only conduct when molten or in solution?

    Metals conduct electricity because delocalised electrons can move freely through the metal lattice at all times.

    Ionic compounds can only conduct when molten or dissolved because in the solid state the ions are in fixed positions and cannot move to carry a charge.

  • In metallic bonding, metal atoms lose outer electrons to form positive ______, while the electrons become ______ and are held by strong ______ forces of attraction.

    In metallic bonding, metal atoms lose outer electrons to form positive ions, while the electrons become delocalised and are held by strong electrostatic forces of attraction.

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