Term 2 part 1

• Different ways to represent covalent bonds:

  • Ven diagram
  • Dots
  • Bond lines
• Macromolecules are giant structures with huge numbers of atoms that are held together
• Limitations of the 2D ball and stick method:

  • Doesn't show shapes of the element
  • Doesn't show correct angles of bonds
• Limitations of the dot and cross method:

  • Shows electrons as different shapes from different elements, but they are the same in reality
  • Electrons are shown as still but are moving
• Forces between covalent bonds are quite weak, meaning it does not need much energy to overcome it
• Intermolecular forces are forces of attraction between molecules
• As size increases, intermolecular forces increase
• Melting/boiling points in larger molecules are high
• Polymers are made up of small reactive molecules that bond with each other
• Compounds can't conduct electricity because they have no overall charge
• Elements cannot be obtained back from compounds
• Elements achieve a stable outer shell through covalent bonding and ionic bonding
• Covalent bonding occurs when non-metals react and share electrons
• Ionic bonding involves the transfer of electrons
• Group 8 elements have similar structures to ions
• Ions can have a positive or negative charge, depending on how many protons and electrons an atom has after losing or gaining an electron
• Ionic bonding works by a metal and non-metal reacting, where an electron from the non-metal goes to the metal, creating stable ions
• Electrostatic forces are forces between oppositely charged ions
• Giant lattices are formed by ionic bonds creating a structure of ions
• Ions formed by each group in ionic bonding:

  • Group 1 forms 1+
  • Group 2 forms 2+
  • Group 3 forms 3+
  • Group 4 does not form ions (except Tn, Pb, and Sn)
  • Group 5 forms 3-
  • Group 6 forms 2-
  • Group 7 forms 1-
  • Group 0 does not form ions
• Ionic bonding between an atom that loses/gains 1 electron and an atom that loses/gains 2 electrons involves having two of the former to give/take 2 electrons to/from the latter
• Ionic compounds have high melting points because a lot of energy is needed to break the bonds
• Molten ionic compounds can conduct electricity as their particles are free and can hold charge, moving to the electrodes
• Ionic compound solutions can conduct electricity as water molecules separate the ions from the lattice, allowing them to hold charge
• Solid ionic compounds cannot conduct electricity as they are strongly bonded together
• Covalent bonds are strong bonds between non-metals