paper 1

• Substances are made of atoms, the different types of which are represented in the periodic table by a symbol
• Compound

  A substance that contains two or more different types of atoms chemically bonded together
• The chemical formula for water is H2O, made up of hydrogen and oxygen atoms with one oxygen atom for every two hydrogen atoms
• If there's no number after a symbol, there is an invisible 1
• Chemical reaction

  Atoms change what they're bonded to and how they're bonded
• Representing a chemical reaction

  1. Word equation

  2. Chemical equation using symbols
• Atoms are not created or destroyed in any chemical reaction, so the same number of each type of atom must be on both sides of the equation
• Balancing a chemical equation

  1. Start with atoms only in compounds

  2. Use numbers in front of elements or compounds to multiply them up
• Atoms

  • Made up of positive and negative charges
  • Positive charge is in the incredibly small nucleus
  • Electrons orbit relatively far away from the nucleus
• Plum pudding model of the atom

  Positive charge with lots of little electrons dotted around it
• Rutherford's model of the atom

  • Positive charge must actually be incredibly small (the nucleus)
  • Electrons must orbit relatively far away from the nucleus
• Bohr's model of the atom

  Electrons exist in shells or orbitals
• Protons

  Positive charges in the nucleus
• Neutrons

  Neutral charges in the nucleus
• Electrons


  Very light negative charges orbiting the nucleus
• Atomic number


  Number of protons in the nucleus
• Mass number


  Number of protons and neutrons in the nucleus
• Isotopes

  Atoms of the same element but with different numbers of neutrons
• Relative abundance


  Percentage of each isotope of an element found in the world
• Periodic table

  Organises elements based on their properties, with gaps for undiscovered elements
• Electron configuration


  The arrangement of electrons in an atom's shells
• Sections of the periodic table

  • Metals (to the left of the staircase)
  • Non-metals (to the right of the staircase)
• Group

  The column an atom is in, indicating how many electrons it has in its outer shell
• Groups of the periodic table

  • Group 1 (alkali metals)
  • Group 7 (halogens)
  • Group 0 (noble gases)
• Ion


  An atom that has gained or lost electrons, no longer neutral
• Charges of ions

  • Group 1 ions are 1+
  • Group 2 ions are 2+
  • Group 7 ions are 1-
  • Group 6 ions are 2-
• Transition metals


  Can donate different numbers of electrons when bonding
• Metallic bonding

  A lattice or grid of metal ions with delocalized electrons around them
• Ionic bonding


  A metal atom donates an electron to a non-metal atom
• Covalent bonding

  Non-metal atoms share electrons to gain full outer shells
• Simple molecular/covalent structures

  Individual molecules that can mix together, with relatively low boiling points
• Giant covalent structures

  One giant molecule made of atoms bonded together, with high melting points
• Allotropes


  Different structures of the same element, e.g. diamond and graphite
• Metal alloys

  Mixtures of metals that are stronger than pure metals
• Credibly strong graphite is only made of carbon as well but it's not Diamond so it's an allotrope of carbon made out of the same atoms bonded together in a different way
• Graphite

  • Consists of layers of carbons with three bonds each in a hexagonal structure
  • The spare delocalized electrons form special weak bonds between the layers which means that it can conduct electricity because the electrons can move between the layers
  • The layers can slide over each other easily which is why it's used in pencils
• Alloy

  A mixture of metals that is stronger than pure metals
• Having mixtures of metals means that we have different size atoms and that disrupts the regular lattice so layers can't slide over each other as easily
• Graphene

  A single layer of graphite
• Fullerenes


  3D structures of carbon atoms, e.g. Buckminster fullerene is a spherical football-like structure consisting of 60 carbon atoms