2. Chemical bonds

• What are the 3 ways atoms can chemically bond

  - ionic- covalent- metallic
• What is ionic bonding?

  Ionic bonding is bonds that have electrostatic attraction. When oppositely charged ions form an ionic bond you get an ionic compound.
• What is a covalent bond?

  A chemical bond formed when two or atoms share electrons.
• What is metallic bonding?


  the chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons
• Cation


  A positively charged ion
• Anion


  A negatively charged ion
• Dot-and-Cross Diagrams


  - all electrons are shown- [ ] + or -
• Empirical Formulae

  [Ca]2+ [F]- [F]-
• E.g of Small molecules

  e.g water
• E.g of large molecules

  E.g. polymers such as polyester and silk.
• E.g of Giant covalent structures

  Diamond, graphite, silicon dioxide
• Ways to represent covalent bonds

  - dot and cross- ball and stick- lines
• Particles in a solid

  - particles are very close together and vibrate in a fixed position.- Solids have a fixed shape and volume.- When heated, the particles vibrate more intensely.
• Particles in a liquid

  - particles are very close together but they move and flow randomly past one another.- has a fixed volume but can change shape and fill a container.
• Particles in a gas

  - particles are far apart and move randomly in all directions.- they change shape and volume to fill whatever container they are in.
• what are the properties of ionic compunds

  - high melting/boiling points- dont conduct electricity if solid- conduct electricty if liquid or in solution
• why would an ionic compound conduct electricity if liquid

  because the ions in the lattice structure can move freely so charge can flow and electricity can be conducted
• why cant ionic compounds not conduct electricity in a solid

  because the ions in the lattice are in a fixed position so charge cant flow
• why do ionic compounds ahve a high melting point

  significant energy is needed to overcome the electrostatic forces between the ions and electrons in the lattice
• the size of the molecule affects the overall

  strength of the intermolecular forces
• properties of small molecules

  - Low boiling point- Very volatile- Flows easily- Ignites easily- dont conduct electricity
• why cant small molecules conduct electricity

  they have no delocalised electrons
• why do small molecueles have low melting points

  the have weak intermolecular forces
• What is a giant covalent structure?

  All the atoms are linked by strong covalent bonds
• Why don't giant covalent structures have a specific formula?

  because the structure can be any size
• Why do giant covalent structures have high melting and boiling points?

  Because lots of energy is needed to break the strong covalent bonds between the atoms
• Why are giant covalent structures insoluble?

  Covalent bonds are too strong to be broken by interaction with solvents
• why are giant covalent structures 1 large molecule

  there's no intermolecular forces
• properties of a pure metal

  - good conductor of heat and electricity- high melting point- malleable- ductile
• Why do metals have high melting and boiling points?

  many strong electrostatic attractions between positive metal ions and delocalised negative electrons, therefore takes a lot of energy to break the strong metallic bonds.
• Why are metals malleable?

  The layers of atoms in a metal can slide over each other
• Why can metals conduct electricity?

  The delocalised electrons can move and carry charge through the metal
• why can metals conduct heat

  The delocalised electrons can carry thermal energy through the structure.
• What is an isotope?

  Atoms of the same element that have different numbers of neutrons
• examples of isotopes

  Carbon-12, Carbon-13, Carbon-14
• What's an allotrope?

  Different forms of the same element
• examples of allotropes

  Carbon (diamond, graphite, and fullerene)
• covalent bonds in dimond

  every carbon atom is bonded to 4 other carbon atoms which makes a giant structure
• why is diamond hard

  each carbon atom is bonded to four others via STRONG covalent bonds
• Does diamond conduct electricity?

  No because it has no free electrons or ions