Whole Topic Cards

• An atom is the smallest part of an element that can exist
• Chemical symbol


  Represents atoms of an element, always starts with a capital letter and consists of one or two letters
• Atoms have a radius of about 0.1 nm (1 * 10-10 m) and the radius of their nucleus is less than 1/10,000 of that of the atom
• Element


  A substance made up of only one type of atom
• Compound


  A substance which contains two or more different elements which are chemically combined in fixed proportions
• Compounds have different properties from the elements that made them
• Compounds can only be separated into elements by chemical reactions, not physical processes
• Writing a chemical reaction

  1. Write the word equation

  2. Write the symbol equation and balance it
• Formulas to know


  • Carbon dioxide is CO2
  • Water is H2O
  • Oxygen is O2
  • Hydrogen is H2
  • Nitrogen is N2
  • Ammonia is NH3
  • Hydrochloric acid is HCl
  • Sulfuric acid is H2SO4
• Subatomic particles


  • Protons (positively charged, in nucleus)
  • Neutrons (neutral, in nucleus)
  • Electrons (negatively charged, in shells)
• Relative charge


  Proton is +1, Neutron is 0, Electron is -1
• Relative mass


  Proton and Neutron are 1, Electron is 1/2000
• Atoms of different elements have different numbers of protons
• Atoms of the same element have the same number of protons
• Isotopes


  Atoms of the same element with the same number of protons but different number of neutrons
• Ion


  A charged particle formed when an atom or molecule gains or loses electrons
• Electron shells/energy levels


  • First shell max 2 electrons
  • Second and third shells max 8 electrons
• Determining subatomic particles in an atom

  1. Find the atomic number to get number of protons

  2. Find the mass number to get number of protons + neutrons

  3. Number of electrons = number of protons
• Determining subatomic particles in an ion

  1. Number of protons = atomic number

  2. Number of neutrons = mass number - atomic number

  3. Number of electrons = atomic number + or - charge of ion
• Relative atomic mass


  The average mass of all the atoms of an element compared to 1/12 the mass of a carbon-12 atom
• Relative atomic masses are often not whole numbers due to the averaging of different isotopes
• Neutrons


  To calculate the number of neutrons, subtract the number of protons from the mass number
• Electrons


  For an ion, the number of electrons is one more than the number of protons to give the overall negative charge
• Relative atomic mass


  The average mass of all the atoms of an element when compared to 1/12 of the mass of a carbon-12 atom
• Relative atomic mass of some elements on the periodic table are not whole numbers because they are averages of several different isotopes
• Calculating relative atomic mass

  Multiply the percentage abundance of each isotope by its mass

  2. Add all these together

  3. Divide by the total abundance (100%)
• Mixture


  Two or more elements or compounds which are not chemically combined
• Methods to separate mixtures

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


  Pour the mixture through filter paper to separate an insoluble solid from a liquid
• Simple distillation


  Heat the solution to evaporate the liquid, then condense the vapour to collect the pure liquid
• Fractional distillation


  Heat the mixture to evaporate the liquid with the lowest boiling point, then condense it in the fractionating column
• Crystallization


  Gently heat the solution to evaporate some of the solvent, then leave to cool and form crystals
• Chromatography


  Place a spot of the mixture on paper, then allow a solvent to soak up the paper and separate the components
• Pencil lines are used in chromatography as they are insoluble in water and many other solvents
• Development of the atomic model

  • Dalton's model
  • Thomson's plum pudding model
  • Rutherford's nuclear model
  • Electron shell model
  • Discovery of protons and neutrons
• Periodic table


  • Columns are called groups, rows are called periods

  Elements in the same group have similar properties and the same number of electrons in the outer shell

  Elements in the same period have the same number of electron shells
• Early periodic tables were incomplete as many elements were unknown at the time
• Mendeleev arranged elements in order of atomic weight but left gaps for undiscovered elements, changing the order in some cases to maintain patterns
• Metals


  Elements that react to form positive ions
• Non-metals


  Elements that react to form negative ions