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AQA A-Level Chemistry New Spec: Bonding

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Bonding Revision for the new AQA Chemistry A-Level specification, as of the 2017 exam eeries

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AQA A-Level Chemistry New Spec: Bonding

  1. 1. Bonding Revision Slides
  2. 2. Ionic Bonding- Metal and Non-Metal Ions Ionic bonding is the transfer of electrons, forming ions, to give full valences. Metals lose electrons to become positive ions and non- metals gain electrons to become negative ions. The opposite charges attract, forming strong forces of electrostatic attraction. Ionic substances form lattices with strong forces of electrostatic attraction between each ion and all its surrounding, oppositely- charged ions. + _
  3. 3. Sodium Atom Chlorine Atom Depiction
  4. 4. Properties of Ionic Compounds • When molten or aqueous, they conduct electricity. This is due to the ions being free and mobile. Therefore, they are able to carry charge through the fluid. • They have high melting and boiling points as they have strong electrostatic forces of attraction inside the lattice. Therefore, a large amount of energy is required to overcome these forces, which is only met at a high temperature. They are always solid at room temperature. • They are brittle and will shatter easily, as a heavy blow to the lattice may cause same-charged ions to come into contact and repel.
  5. 5. Covalent Bonding- Multiple Non-Metals Covalent bonding is the sharing of electrons between atoms, to give full outer shells. In a bond, electrons may sometimes be attracted to one atom more than the other, due to a significantly higher nuclear charge and electronegativity, forming partial negative (δ-) and partial positive (δ+) charges in a polar bond. The electrons in the bond are in pairs, and each atom now has a noble gas arrangement. Macromolecules are much larger covalent compounds and have vastly different properties to simple molecular compounds.
  6. 6. O Depiction
  7. 7. Properties of Molecular Covalent Compounds • They have a very low melting and boiling point due to the fact they have very weak intermolecular van der Waals forces. Many are gases at room temperature. Water, however, has hydrogen bonding and is thus a liquid between 0 and 100˚C. • They are very poor conductors, even when aqueous or molten because they have neutral charges and so they cannot carry a current.
  8. 8. Properties of Macromolecular Covalent Compounds • They have very high melting and boiling points as they have very strong intramolecular covalent bonds which require large amounts of energy to be overcome. However, they have very weak intermolecular forces. • Graphite, only, will conduct as it has electrons between its layers that can carry current.
  9. 9. Dative Covalent Bonds Dative covalent bonds are formed when both electrons in a bonding pair are donated by one of the atoms, only. In a dative covalent bond, the atom that does not provide electrons doesn’t have a filled outer shell of electrons and is electron deficient. The atom that provides the electrons has a lone pair.
  10. 10. Metallic Bonds- Metals Metallic bonding is the donation of all valence electrons to the delocalised ‘sea’ of electrons, forming positive metal ions, with full outer shells. The opposite charges attract, forming strong forces of electrostatic attraction, like in ionic compounds. Metal ions are held in a regular structure, with a constantly moving sea, moving from areas of high negativity to areas of high positivity.
  11. 11. Depiction e e e e e e e e e e e e e
  12. 12. Properties of Metals • They are highly conductive of heat and electricity as the delocalised electrons can move through the structure. As they do, they can carry the current through, or, in the case of heat, collide with ions further along the structure, giving them more energy, increasing the rate at which heat moves along the structure. • They are very strong due to high electrostatic forces of attraction between ions and electrons. • They are malleable as the ion layers can slide over each other, whilst still remaining attracted to the structure, retaining the strength of the metal. • Their melting and boiling points are high, as it requires a large amount of energy to separate the structure, due to both strong forces of attraction and the size of the structure.

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