History of the atom

• John Daltons theory

  He describes atoms as solid spheres and also said that different sized spheres made up different elements
• J J Thompsons finding and theory

  He found that atoms contain even smaller negatively charged particles (electrons)

  Proposed that the atom was a ball of positive charge with discrete electron’s throughout (plum pudding model)
• Rutherford

  Conducted alpha particle scattering

  Found that some alpha particles passed straight through the sheet of gold but some were deflected away or backwards
• Nuclear model of the atom

  Proposed by Rutherford

  The idea that each atom is composed of a small positively charged nucleus at the centre, surrounding by a cloud of negative electrons
• Main issue with the nuclear model of atom

  The electrons should be attracted to the positive nucleus, so the atom should just collapse
• Neil’s Bohr

  Suggested that electrons orbit the nucleus in shells
• James Chadwick

  Discovered neutral particles called neutrons