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Ionic Metallic Covalent Macromolecular / giant covalent Graphite Molecular / simple covalent Diamond Diagram of structure Describe how the bonds are formed Melting point & why? Electrical conductivity & why? Solubility & why? Activity 1 - Structure and properties research task
ANSWERS Ionic Sodium chloride Metallic Sodium Covalent Giant covalent Graphite Diamond Outer-shell electrons are delocalised to the bulk. Electrostatic attractions between the delocalised electrons and the metal ions and electrostatic repulsions between electrons and between the metal ions. Each carbon forms three covalent bonds with three other carbon atoms (sharing of two outer-shell electrons). The fourth electron is delocalised across the graphite layer. Each carbon forms four single covalent bonds with four other carbon atoms (sharing of two outershell electrons). Simple covalent Iodine Diagram of structure Describe how the bonds are formed 1 electron transferred from a sodium atom to a chlorine atom to make Na+ and Cl–. Electrostatic attraction between ions of opposite charge and electrostatic repulsion between ions of similar charge. A single covalent bond exists between iodine atoms, with each atom sharing one electron each. Weak intermolecular forces between adjacent iodine molecules. Weak intermolecular forces between adjacent layers. Melting point & why? High because the strong electrostatic forces of attraction between oppositely charged ions require large amounts of energy (hence high temperature) to break. High, because the strong electrostatic forces of attraction between the metal ions and the electrons require large amounts of energy (hence high temperature) to break. High, because it is a giant lattice and large amounts of energy (hence high temperature) are required to break the strong covalent bonds. Low, as the intermolecular forces between the molecules are weak, so require little energy (hence low temperature) to break. Electrical conductivity & why? Conducts electricity in liquid state and in solution due to the flow of ions. Conducts electricity in the solid and molten state, due to flow of delocalised electrons. Conducts electricity in the solid state due to the flow of delocalised electrons. Does not conduct electricity – electrons are localised in covalent bonds. Solubility in water & why? Soluble: ions can form bonds with the polar water molecules. Insoluble as not polar. Slightly soluble in water as induced dipoles in iodine can form bonds with polar water molecules.