Chemistry topic 2

• Compounds are substances in which 2 or more elements are chemically combined
• There are 3 types of strong chemical bonds: ionic, covalent and metallic
• Ionic bonding:

  • Particles are oppositely charged ions
  • Occurs in compounds formed from metals combined with non-metals
  • Metal atoms lose electrons to become positively charged ions
  • Non-metal atoms gain electrons to become negatively charged ions
  • Ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 gains full outer shell of electrons, similar to noble gases
  • Electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram
• Ionic compounds:

  • A giant structure of ions
  • Held together by strong electrostatic forces of attraction between oppositely charged ions
  • Forces act in every direction due to the 3D structure
  • Example: sodium chloride (salt) with Na+ (small blue particles) and Cl- (larger green ones)
• Covalent bonding is when atoms share one or more pairs of electrons
• Polymers are large covalently bonded molecules
• Metallic bonding:

  • Consists of positive ions and delocalised electrons arranged in a regular pattern
  • Delocalised electron system consists of electrons 'lost' from the atoms to form positive ions
  • Delocalised electrons are free to move through the structure
  • Shared delocalised electrons make metallic bonds strong
• Covalent bond:

  • A shared pair of electrons between two non-metals
• Electrostatic forces:

  • The strong forces of attraction between oppositely charged ions
• Empirical formula:

  • The smallest whole number ratio of atoms of each element in a compound
• Fullerenes:

  • Molecules of carbon atoms with hollow shapes, based on hexagonal rings of carbon atoms but may also contain rings with five or seven carbon atoms
• Graphene:

  • A single layer of graphite with properties useful in electronics and composites
• Graphite:

  • A giant covalent structure made up of carbon atoms, each forming three covalent bonds with three other carbon atoms, forming layers of hexagonal rings with no covalent bonds between the layers
• Ionic compound:

  • Chemical compound formed of ions, held together by strong electrostatic forces
• Ionic bond:

  • A metal atom loses electron(s) to form a positively charged ion and a non-metal gains these electron(s) to form a negatively charged ion. An ionic bond is formed between the oppositely charged ions
• Metals:

  • Elements that react to form positive ions, found to the left and towards the bottom of the periodic table
• Non-metals:

  • Elements that react to form negative ions, found towards the right and top of the periodic table
• Particle theory:

  • Models the three states of matter by representing particles as small solid spheres. Helps explain melting, boiling, freezing, and condensing
• Polymers:

  • Large long-chain molecules made up of lots of small monomers joined together by covalent bonds
• Repeat unit:

  • The part of a polymer whose repetition would produce the complete polymer chain
• State symbols:

  • Symbols used in chemical equations to denote the states of the chemicals reacting: (s) - solid, (l) - liquid, (g) - gas, (aq) - aqueous solution
• Ionic bonding consists of

  Oppositely charged particles