The Atom

• What is an atom?

  Smallest part of an element that can exist
• What is Dalton’s model of the atom?

  Atoms as solid spheres that could not be divided into smaller parts
• What is the plum pudding model of the atom?

  A sphere of positive charge with negative electrons embedded in it
• What did scientists discover in the alpha scattering experiment?

  Some alpha particles were deflected by the gold foil

  • this shows that an atom’s mass and positive charge must be concentrated in one small space
  • this was called the nucleus
• Describe the nuclear model of the atom

  A dense nucleus with electrons orbiting it
• What did Niles Bohr discover?

  That electrons orbit at fixed energy levels

  • Called shells
• What did James Chadwick discover?

  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 (very small)
• 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?

  the atomic number on the periodic table
• How can you calculate the number of neutrons in an atom?

  mass number - atomic number = neutron number
• Why do atoms have no overall charge?

  There are equal numbers of positive protons and negative electrons
• What is an element?

  A substance made of only one type of atom
• What is a compound?

  A substance made of two or more types of atom that are chemically combined
• What is a mixture?

  Two or more substances that are not chemically combined
• What are the four physical processes that can be used to separate a mixture?

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

  The average mass of all the atoms of an element.
• What is filtration used for?

  To separate an insoluble solid and a liquid
• What is crystallisation used for?

  Separating a soluble solid from a solution
• What is simple distilation?

  Separating a solvent from a solution
• What is fractional distillation?

  Separating two liquids with similar boiling points
• What is paper chromatography?

  Identifying substances from a mixture in solution