GCSE AQA Chemistry 2 Bonding

GCSE AQA Chemistry 2 Bonding

1. Atoms

   • Mass no. -> total no. of protons and neutrons
     • Electrons not counted because their mass is negligible
   • Atomic no. -> no. of protons
   • Compounds
     • Atoms of two or more elements are chemically combined

2. Isotopes

   • Different atomic forms of the same element which have the same no. of protons but a different no. of neutrons
   • Same atomic no. but different mass no.

3. Ionic Bonding

   • Atoms gain/lose electrons to form charged particles (ions)
     • Strongly attracted to each other
   • Shells with 1/2 outer electrons want to get rid so left with full shells
     • Metals lose to form positive ions
   • Nearly full shells want to gain to get full shell
     • Non-metals gain to form negative ions
   • Ionic compounds
     • Giant regular ionic lattice structure
       • Strong electrostatic forces of attraction between oppositely charged ions
     • Properties - high melting & boiling points, will carry electric current when molten & dissolve easily in water

4. Covalent Bonding

   • Sharing electrons
     • In their outer shells
   • Both atoms feel like they have a full outer shell
   • Non-metals only
   • Covalent substances
     • Simple Molecular
       • Atoms form strong CBs to form small molecules
         • Intermolecular forces - v. weak
           • Melting & boiling points v. low - bonds easily broken
       • Most are gases/liquids at rm. temp.
       • Don't conduct electricity
     • Giant Covalent Structures (Macromolecules)
       • All atoms bonded to each other by strong CBs
         • V. high melting/boiling points
       • Don't conduct electricity
       • Examples:
         • Diamond
           • Forms 4 CBs
             • Hardest natural substance
         • Graphite
           • Forms 3 CBs
             • Creates layers - free to slide
               • Weak intermolecular forces between layers
           • Only non-metal - good conductor of heat/electricity
             • Each atom has one delocalised electron
         • Silicon dioxide (Silica)
           • Giant structure of silicon & oxygen

5. Metallic Structures

   • Giant structure
   • Delocalised electrons - come from outer shell of every metal atom
     • Free to move - good conductors of heat/electricity
     • Hold atoms in regular structure
       • Strong forces of electrostatic attraction between positive metal ions & negative electrons
     • Layers of atoms can slide - metals can be bent/shaped
   • Alloys
     • Mixture of 2 or more metals
     • Different elements have different sized atoms
       • Layers distorted - hard to slide so alloys are harder