Paper 1

• Atom


  The smallest part of an element that can exist
• Element

  A substance of only one type of atom
• There are approximately 100 elements listed in the periodic table
• Groups of elements based on properties

  • Metals
  • Non-metals
• Compound

  Two or more elements combined chemically in fixed proportions which can be represented by formulae
• Compounds have different properties than their constituent elements
• Mixture

  Two or more elements or compounds not chemically combined together
• Mixtures have the same chemical properties as their constituent materials
• Methods to separate mixtures

  • Filtration
  • Crystallisation
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Separation methods for mixtures do not involve chemical reactions
• Simple distillation

  1. Liquid boils off and condenses in the condenser

  2. Thermometer reads the boiling point of the pure liquid
• Crystallisation/Evaporation

  1. Solution is heated until all solvent evaporates

  2. Saturated solution is cooled to form crystals

  3. Crystals are collected via filtration
• Fractional distillation

  1. Mixture is repeatedly condensed and vaporised

  2. Fractionating column separates compounds based on different boiling points
• Filtration

  1. Insoluble solid (residue) is caught in the filter paper

  2. Filtrate is the substance that comes through the filter paper
• Chromatography

  1. Mixture is dissolved in solvent and placed on paper

  2. Solvent rises, separating the mixture into its components
• Separating funnel

  Apparatus for separating immiscible liquids of different densities
• Plum-pudding model

  Atom is a ball of positive charge with negative electrons embedded in it
• Bohr/nuclear model

  Electrons orbit the nucleus at specific distances (shells) - came from alpha scattering experiments
• Proton

  Smaller, positive particle discovered in the nucleus
• Neutron

  Particle discovered in the nucleus by James Chadwick
• Atom structure

  Small central nucleus (protons and neutrons) with electrons orbiting
• Masses: Proton 1, Neutron 1, Electron very small; Charges: Proton 1, Neutron 0, Electron -1
• Electrical neutrality of atoms

  Equal number of electrons and protons
• Radius of an atom is 0.1 nm
• Radius of a nucleus is 1 x 10-14 m, 1/10000 of the atom radius
• Atomic number

  Number of protons in the nucleus
• Atoms of the same element have the same number of protons in the nucleus
• Majority of an atom's mass is in the nucleus
• Mass number

  Total number of protons and neutrons
• Calculating number of neutrons


  Subtract atomic number from mass number
• Isotope

  Atoms of the same element with different numbers of neutrons, but same chemical properties
• Relative atomic mass

  Average mass value taking into account the mass and abundance of isotopes
• Electronic configurations

  • He: 2
  • Be: 2,2
  • F: 2,7
  • Na: 2,8,1
  • Ca: 2,8,8,2
• Ion

  Atom or molecule with an unequal number of electrons and protons
• Isotopes

  Atoms of the same element that have a different number of neutrons
• Relative atomic mass

  The average mass value which takes the mass and abundance of isotopes of an element into account, on a scale where the mass of 12C is 12
• Electronic configurations

  • He (2)
  • Be (4)
  • F (9)
  • Na (11)
  • Ca (20)
• Ions

  Charged particles formed when atoms lose electrons (positive ions) or gain electrons (negative ions)
• When a metal reacts with a non-metal, an ionic compound is formed
• When a non-metal reacts with a non-metal, a molecular compound is formed