Chemistry

• Ionic bonding is the transfer of electrons from metal atoms to non-metals atoms (attraction between opposite charged ions)
• S: strong

  E: electrostatic

  A: attraction

  B: between

  O: opposite

  C: charged

  I: ions
• They lose or gain electrons to form full outer shells. Metals always form positive ions and non-metals always form negative ions
• To find the formula of an ionic compound, you balance the positive and negative charges e.g. NaCl
• Ionic compounds always have giant ionic lattice structures, with opposite charged ions held together by strong electrostatic forces of attraction
• Ionic compounds all have similar properties
• Ionic compounds have HIGH melting/boiling points due to strong attraction between ions since it takes large amounts of energy to overcome this attraction
• Solid ionic compounds don’t conduct electricity because the ions are fixed in place and can’t move but when the compound melts the ions can move and will carry a charge
• Ionic compounds also dissolve easily in water. The ions separate and are all free to move in the solution so they’ll carry an electric charge
• Covalent bonds are when non-metal atoms share electrons with each other to form a covalent bond Which makes both atoms have full outer shells
• Each covalent bond provides one extra shared electron for each atom
• Covalent bonds are strong because there’s a strong electrostatic attraction between the positive nuclei of atoms and negative electrons in each shared pair
• Simple molecular substance have LOW melting and boiling points
• Substances formed with covalent bonds usually have simple covalent structures and the atoms within the molecules are help together by very strong covalent bonds
• The forces of attraction between these molecules are very weak.
• The melting/boiling points are very low because the molecules are easily parted from eachother
• Most simple molecular substances are gases or liquids at room temperature and simple molecular substances don’t conduct electricity because they don’t have free electrons
• Giant covalent structures are similar to giant ionic lattices except there are no charged ions
• The atoms are bonded to eachother by strong covalent bonds so they have very high melting and boiling points
• They don’t conduct electricity (except graphite, grapheme and fullerenes)
• The examples needed are made from carbon atoms, carbon can form lots of different types of molecule because carbon can form up to 4 covalent bonds and bond easily to other carbon atoms to make chains and rings
• Pure diamonds are lustrous and colourless.
• Each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure, which makes diamond really hard making them ideal for cutting tools
• All those strong covalent bonds take a lot of energy to break and give diamond an extremely high melting point
• It also doesn’t conduct electricity because there are no free electrons
• Graphite is black And opaque but still shiny. Each carbon atom only forms three covalent bonds creating sheets of carbon atoms which are free to slide over each other
• The layers are held together weakly so they are slippery and can be rubbed off onto paper to leave a black mark like a pencil. graphite has a high melting point - the covalent bonds need lots of energy to break
• Since only 3 out of each carbon 4 outer electrons are used in bonds there are lots of delocalised electrons that can move. This means graphite can conduct electricity
• Graphene is a single sheet of graphite. Its covalent bonds make it extremely sting and the sheet is so thin it’s transparent and light
• It’s delocalised electrons are completely free to move so it’s a better conductor than graphite
• Fullerenes are another form of carbon, they aren’t giant covalent structures they’re large molecule. different fullerenes contain different numbers of carbon atoms
• The carbon atoms in fullerenes are arranged in rings, similar to those in graphite and like graphite they have delocalised electrons so they can conduct electricity
• They don’t have as high melting/boiling points as diamond or graphite but they are high for a molecular substance
• Nanoparticles


  Really tiny particles, 1-100 nanometres across
• Nanoparticles contain roughly a few hundred atoms, so they're bigger than atoms but smaller than pretty much anything else
• Nanoparticles


  • Fullerenes
  • Nanotubes
• Nanotubes


  • Made of covalent bonds, very strong
• Nanoparticles


  Have very different properties from the 'bulk' chemical that they're made from
• Nanoparticles


  • Have a high surface area to volume ratio
• As particles decrease in size, the size of their surface area increases in relation to their volume so their surface area to volume ratio increases