The Atom

• What is an atom?

  The smallest part of an element that can exist.
• What is John Dalton's model of the atom?

  Atoms as solid spheres that couldn't be divided into smaller parts.
• What is the plum pudding model of the atom?

  Sphere of positive charge with negative electrons embedded into it.
• What did scientists discover in the alpha scattering experiment?

  Some alpha particles were deflected by the gold foil, this showed that an atom's mass and positive charge must be concentrated in one small space (the nucleus).
• Describe the nuclear model of the atom.

  Dense nucleus with electrons orbiting it.
• What did Niels Bohr discover?

  Electrons orbit in fixed energy levels (shells).
• What did James Chadwick discover?


  Uncharged particle called the neutron.
• Where are protons and neutrons?

  In the nucleus.
• What is the relative mass of each sub-atomic particle?

  Proton: 1 Neutron: 1 Electron: 0
• What is the relative charge of each sub-atomic particle?

  Proton: +1 Neutron: 0 Electron: -1
• How can you find out the number of protons in an atom?

  Atomic number in the periodic table.
• How can you calculate the number of neutrons in an atom?

  mass number - atomic number
• What do atoms have no overall charge?

  Equal numbers of positive protons and negative electrons.
• How many electrons would you place in the 1st, 2nd and 3rd shells?

  2,8,8
• What is an element?


  Substance that is made up of one atom.
• What is a compound?


  Substance made up of more than one type of atom, chemically joined together.
• What is a mixture?

  Two or more substances not chemically combined.
• What are isotopes?

  Atoms of the same element (protons) with different numbers of neutrons.
• What are the 5 physical processes that can be used to separate mixtures?

  Filtration, crystallisation, distillation, fractional distillation and chromatography.
• What is relative mass?

  The average mass of all the atoms of an element.