Chemistry Paper 1

• Element

  The smallest part of an element that can exist and still be that element
• Compound


  Formed when elements combine together in chemical reactions, contains two or more elements chemically combined in fixed proportions
• Naming compounds from their formula

  1. Take the name of the metal and leave it as it is

  2. Take the first syllable of the name of the nonmetal

  3. Add 'ide' on the end

  4. If there are three elements and one is oxygen, add 'ate' on the end
• Mixture


  Two or more elements or compounds that are not chemically combined together, they are not bonded
• Physical separation processes


  • Filtration
  • Crystallization
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Fractional distillation


  • Separates a mixture of liquids according to their boiling points
  • Uses a fractionating column with a temperature gradient
• Chromatography


  • Separates a mixture based on the solubility of its components
  • Uses a stationary phase and a mobile phase
• Atom


  Smallest part of an element that can exist and still be that element, contains protons, neutrons and electrons
• The nucleus is only one ten thousandth of the diameter of the atom
• The relative mass of the electron is not zero, it is about one over 1840
• Isotopes


  Atoms of the same element that have different numbers of neutrons
• Calculating relative atomic mass of a sample with isotopes

  1. Find the percentage of each isotope

  2. Multiply the mass of each isotope by its percentage

  3. Add the results together
• Atomic models


  • Dalton model - atoms are indivisible spheres
  • Thomson model - atoms have electrons embedded in a positive charge
  • Rutherford model - atoms have a tiny dense nucleus surrounded by electrons
  • Bohr model - electrons orbit the nucleus in distinct shells
  • Modern model - nucleus contains protons and neutrons
• Periodic table


  • Arranged in order of atomic number (number of protons)
  • Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell
• The periodic table was originally arranged by atomic weight, which led to some issues
• Electrons in outer shell


  Determines how an element reacts with other elements
• The periodic table hasn't always been laid out like this
• Initially, elements were arranged according to their atomic weight, which led to some problems
• Dmitri Mendeleev left gaps in the periodic table and made predictions about undiscovered elements, which turned out to be correct
• Metals


  Elements that will react to form positive ions
• Nonmetals


  Elements that will react but won't form positive ions
• Metals


  • Malleable (can be hammered into shape)
  • Conductive (conduct heat and electricity)
  • Generally have high melting points
• Group 1 (Alkali metals)


  Highly reactive metals that react violently with water
• Alkali metals are usually kept under oil to stop them from reacting with oxygen
• Group 7 (Halogens)


  Elements with 7 electrons in their outer shell, exist as diatomic molecules
• Halogens in group 7


  Become more reactive as you go up the group, can displace halogens lower in the group
• Group 0 (Noble gases)

  Elements with full outer shells, very stable and unreactive
• Boiling points of noble gases

  Increase as you go down the group, due to stronger intermolecular forces
• Metallic bonding


  Positive metal ions surrounded by a sea of delocalized electrons, held together by strong electrostatic forces
• Alloys


  Mixtures of metals or metals and carbon, distorted structure makes them harder than pure metals
• Ionic bonding


  Transfer of electrons from metal to nonmetal, forming positive and negative ions that are held together in a giant ionic lattice
• Covalent bonding


  Sharing of electron pairs between nonmetal atoms
• Types of covalent substances

  • Small covalent molecules
  • Giant covalent structures
• Polymers


  Very long chains of repeating monomer units, held together by strong covalent bonds
• Giant covalent structures are made up of thousands of atoms held together by strong covalent bonds
• Polymers


  Very long chains of repeating units called monomers, held together by strong covalent bonds
• Monomers


  Repeating units that make up polymers, held together by strong covalent bonds
• Intermolecular forces


  Weak forces between polymer chains, not as strong as covalent or ionic bonds
• Giant covalent structures


  • Diamond
  • Graphite
  • Graphene
  • Fullerenes
  • Silicon dioxide
• Diamond


  • Every carbon atom makes four strong covalent bonds
  • Incredibly hard
  • Does not conduct electricity