C1 structure&bonding

• Electrons


  Exist in energy levels or shells
• Maximum electrons per energy level


  • First energy level: 2
  • Second energy level: 8
  • Third energy level: 8
• Noble gases


  Have a full outer energy level
• Noble gases


  Are unreactive
• Ionic bonding


  Occurs when a metal reacts with a non-metal
• Ionic bonding between lithium and fluorine

  1. Lithium atom loses outer electron

  2. Fluorine atom gains electron

  3. Both atoms achieve full outer energy level
• Lithium ion


  Atom with 3 protons and 2 electrons, overall +1 charge
• Fluoride ion


  Atom with 9 protons and 10 electrons, overall -1 charge
• During ionic bonding, group 1 metals lose 1 electron forming a +1 ion, and group 7 non-metals gain 1 electron forming a -1 ion
• Both ions have a full outer energy level, the stable electronic structure of a noble gas
• Ionic bonding


  • Sodium and chlorine
• Ionic bonding between sodium and chlorine

  1. 1 electron passes from sodium atom to chlorine atom

  2. Both atoms achieve full outer energy level
• Ionic bonding


  Occurs when a metal reacts with a non-metal
• Electron transfer in ionic bonding between group two metals and group six non-metals

  1. Group two metal loses two electrons

  2. Electrons transferred to group six non-metal

  3. Group two metal forms positive ion

  4. Group six non-metal forms negative ion

  5. Both ions have full outer energy level (stable electronic structure of noble gas)
• Ionic bonding


  • Group two metals lose two electrons
  • Group six non-metals gain two electrons
  • Both ions have full outer energy level (stable electronic structure of noble gas)
• In dot and cross diagrams, only the outer energy levels are shown as they are involved in the reaction
• In exams, you could be asked to show ionic bonding between any metal in group 1 or 2 and any non-metal in group 6 or 7
• Ionic compounds


  Form giant ionic lattices
• Giant ionic lattice


  • Every positive ion is surrounded by negative ions
  • Every negative ion is surrounded by positive ions
  • Three-dimensional structure
• Electrostatic forces of attraction

  • Strong forces of attraction between positive and negative ions
  • Also called ionic bonds
  • Act in all directions
• Heating an ionic solid

  Particles vibrate with enough energy to break the electrostatic forces of attraction, causing the solid to melt
• Melting and boiling points of ionic compounds

  Very high due to the strong electrostatic forces of attraction requiring a great deal of heat energy to break
• Sodium chloride has a melting point of around 800°C
• Ionic compounds cannot conduct electricity when solid

  Ions are locked in place by strong electrostatic forces of attraction, can only vibrate but not move
• Ionic compounds can conduct electricity when molten or dissolved in water


  Ions can now move and carry the electrical charge
• When ionic compounds conduct electricity, it is the ions that are moving, not electrons
• Covalent bonding


  Bonding that occurs when non-metal atoms share electrons
• Covalent bonding in hydrogen molecule (H2)

  1. Hydrogen atoms overlap their energy levels

  2. Hydrogen atoms share a pair of electrons

  3. Both hydrogen atoms achieve a full outer energy level
• Covalent bond


  • A strong bond formed by the sharing of a pair of electrons
• Covalent bonding in chlorine molecule (Cl2)

  1. Chlorine atoms overlap their outer energy levels

  2. Chlorine atoms share a pair of electrons

  3. Both chlorine atoms achieve a full outer energy level
• Covalent bonding in hydrogen chloride (HCl)

  1. Hydrogen and chlorine atoms overlap their outer energy levels

  2. Hydrogen and chlorine atoms share a pair of electrons

  3. Both atoms achieve a full outer energy level
• Hydrogen and chlorine are non-metal elements
• Covalent bonding occurs between non-metal atoms
• Covalent bonding produces molecules where atoms share electrons to achieve a full outer energy level
• Small covalent molecules


  Molecules with a small number of atoms, e.g. methane with 5 atoms
• Small covalent molecules


  • Have low melting and boiling points
  • Are usually gases or liquids at room temperature
• Small covalent molecules


  • Methane
  • Other molecules shown
• Water is a liquid at room temperature, but has a relatively low boiling point of 100°C
• Why small covalent molecules have low melting and boiling points

  1. Atoms in each molecule held together by strong covalent bonds

  2. Weak intermolecular forces between molecules

  3. As temperature increases, vibration of molecules increases

  4. At a certain point, vibration is strong enough to break weak intermolecular forces, causing molecules to turn to a gas (boil)
• Covalent bonds are not broken when a substance melts or boils