structure and bonding

• Solids


  • Extremely hard to compress
  • Fixed shape, cannot flow
• Liquids


  • Extremely hard to compress
  • Take shape of container, can flow
• Gases


  • Extremely easy to compress
  • Spread out and fill container, move quickly and randomly
• Melting


  1. Heating a solid to change it to a liquid

  2. Particles in liquid have more kinetic energy than solid

  3. Energy needed to break forces of attraction between solid particles
• Stronger forces of attraction between particles

  Higher melting point
• Freezing


  1. Cooling a liquid to change it to a solid

  2. Forces of attraction between particles reform
• Boiling


  1. Heating a liquid to change it to a gas

  2. Energy needed to break forces of attraction between liquid particles
• Condensing


  1. Cooling a gas to change it to a liquid

  2. Forces of attraction between particles reform
• Boiling point and condensing point are the same temperature
• Limitations of simple particle model

  • Assumes particles are solid spheres (not true)
  • Assumes no forces between particles (not true)
• Electrons


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

  • First energy level: 2 electrons
  • Second energy level: 8 electrons
  • Third energy level: 8 electrons
• Noble gases (group 0)

  • Have a full outer energy level
  • Are stable
  • Are unreactive
• Ionic bonding


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

  1. Lithium atom loses 1 electron

  2. Fluorine atom gains 1 electron

  3. Both atoms achieve a full outer energy level
• Ion


  An atom with an overall charge
• Ions formed


  • Lithium ion (1+ charge)
  • Fluoride ion (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 now have a full outer energy level, the stable electronic structure of a noble gas
• The question asks to describe what is happening in the reaction between sodium (group 1) and chlorine (group 7)
• Ionic bonding between sodium and chlorine

  1. 1 electron passes from sodium atom to chlorine atom

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


  Occurs when a metal reacts with a non-metal
• Ionic bonding between group 2 metals and group 6 non-metals

  1. Metal atom loses 2 electrons

  2. Non-metal atom gains 2 electrons

  3. Metal forms 2+ ion

  4. Non-metal forms 2- ion

  5. Both ions have full outer energy level
• Magnesium atom


  12 protons, 12 electrons (neutral)
• Magnesium reacting with oxygen


  1. Magnesium atom loses 2 electrons

  2. Oxygen atom gains 2 electrons

  3. Magnesium forms 2+ ion

  4. Oxygen forms 2- ion (oxide ion)

  5. Both ions have full outer energy level
• Dot and cross diagram can be used to show ionic bonding
• Other ionic bonding reactions

  • Lithium and oxygen
  • Calcium and fluorine
• In ionic bonding, group 1 or 2 metals lose electrons to form positive ions, and group 6 or 7 non-metals gain electrons to form negative ions
• Ionic compound


  A compound formed by the transfer of electrons from a metal to a non-metal
• 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
• Ionic compounds have high melting and boiling points


  Because the strong electrostatic forces of attraction require a great deal of heat energy to break
• Melting of ionic solids

  1. Particles vibrate

  2. Electrostatic forces of attraction 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
• Ionic compounds can conduct electricity when molten or dissolved in water


  Ions can now move and carry the electrical charge
• It is the ions that move, not electrons, when ionic compounds conduct electricity
• Covalent bonding


  Electrons are shared between non-metal atoms to achieve a full outer energy level
• Hydrogen molecule (H2)


  • Two hydrogen atoms bond by sharing a pair of electrons
  • Both atoms have a full outer energy level like a noble gas
• Chlorine molecule (Cl2)


  • Two chlorine atoms bond by sharing a pair of electrons
  • Both atoms have a full outer energy level like a noble gas