GCSE Chemistry

• Compound name if it has a metal and non-metal:

  • Name of the metal first, then non-metal with -ide ending
• Compound name if made of 2 non-metals:

  • If there is hydrogen, it goes first, or the one with lower group number comes first, then name of other non-metal with -ide ending
• Symbol equation for a compound is related to the structure of the compound
• Symbol equations for compounds with giant structures tell you the ratio of the atoms
• Symbol equations for molecular compounds tell you exactly how many atoms are bonded together
• Valency of an element is how many electrons move to form a compound
• To find the valency of an element:

  • Group 1 - 1
  • Group 2 - 2
  • Group 3 - 3
  • Group 4 - 4
  • Group 5 - 3
  • Group 6 - 2
  • Group 7 - 1
  • Group 0 - Don't form compounds
  • Hydrogen - 1
  • Transition elements - Depends on the element
• Symbol equation for a compound using valencies:

  • Write the valencies of the two elements
  • Write down their symbols, in the order the compound is written in
  • Add numbers to balance the valencies
• Chromatograms are the chromatography paper used to show the separation of colors
• Radius of an atom is 0.1nm
• Nucleus:

  • Middle of the atom
  • Has protons and neutrons
  • Radius = 1 x 10^-14 (1/10,000 of an atom)
  • Mass concentrated around the nucleus
• Electrons:

  • Move around the nucleus
  • Negatively charged and covers a lot of space
  • Volume of orbits depends on the size
  • No mass
• Atoms are neutral because they have the same number of protons and electrons
• Atoms are not neutral in ions because the amount of protons are not equal to the amount of electrons
• Nuclear symbol is a symbol that indicates the mass number and atomic number of an element
• Atomic mass is the number of protons and neutrons
• Atomic number is the number of protons
• Number of neutrons is calculated by mass number - atomic number
• Isotopes are different forms of an element where the number of protons is the same but the number of neutrons is different. They have the same atomic mass but different atomic number
• Relative Atomic Mass is the average atomic mass of an element
• RAM formula:

  • (isotope abundance x isotope mass) + (isotope abundance x isotope mass)/Sum of all isotope abundance
• Mixtures do not have chemical bonds
• Mixtures are separated using physical methods
• Air is a mixture of gases
• Crude oil is a mixture of hydrocarbon molecules
• Chemical properties do not change in mixtures
• Chromatography works by:

  • Drawing a line at the bottom of the page
  • Adding a dot of ink on the line
  • Some need a solvent in the water
  • Making sure the ink does not touch the paper
  • The dye travels up the paper at different times
  • If a dye is insoluble, it stays at the base line
• Filtration is separating insoluble solids from liquids
• Two ways of separating soluble solids from liquids are evaporation and crystallization
• Evaporation:

  • Pour solution onto an evaporating dish
  • Slowly heat solution, the solvent will start to evaporate
  • Dry crystals will be seen
• Crystallization:

  • Pour Mixture onto an evaporating dish
  • When crystals form, leave it to cool
  • Salt starts to form crystals
  • Filter crystals
• Simple distillation is separating a liquid from a solid
• Distillation works by:

  • Heating the solution, the liquid with the lowest boiling point evaporates
  • Vapour condenses and is collected
• Disadvantage of using simple distillation is it can only be used to separate liquids with different boiling points because vapor can sometimes be given off before the boiling point is reached
• Dalton said atoms were solid spheres
• Thomson discovered electrons by doing the cathode ray experiment, where he put atoms in a tube, particles in the would go to the positive charge, lighting the positive charge up. This meant there were negative charges in the atom
• Plum pudding model is a model of an atom where the atom is a ball of positive energy with electrons stuck underneath it
• Rutherford and Marsden disproved the plum pudding model by firing alpha particles at gold foil
• If the plum pudding model was correct, alpha particles fired at the gold foil would have gone through the atom or deflected slightly as most of the atom was positively charged
• Nuclear model is a positively charged nucleus surrounded by a sea of negative electrons