• The mass of an atom is?concentrated?in the nucleus, because the nucleus contains the heaviest subatomic particles (the neutrons and protons)
  • The mass of the electron is negligible
• The nucleus is also?positively?charged?due to the protons
• Electrons orbit the nucleus of the atom, contributing very little to its overall mass, but creating a?‘cloud’?of negative charge
• The?electrostatic?attraction?between the?positive nucleus?and?negatively charged electrons?orbiting around it is what holds an atom together

The mass of the atom is concentrated in the positively charged nucleus which is attracted to the negatively charged electrons orbiting around it

• Protons, neutrons and electrons behave differently when they move at the same?velocity?in an?electric field
• When a beam of?electrons?is fired past the?electrically charged plates, the electrons are deflected?very easily?away?from the negative plate towards the?positive plate
  • This proves that the electrons are?negatively?charged; like charges repel each other
  • It also shows that electrons have a?very small mass,?as they are easily deflected
• A beam of?protons?is deflected?away?from the positive plate and towards the?negative plate
  • This proves that the proton is?positively charged
  • As protons are deflected less than electrons, this also shows that protons are?heavier?than electrons
• A beam of neutrons is not deflected at all
  • Which proves that the particle is?neutral?in character; it is not attracted to, or repelled by, the?negative?or?positive?plate

The lighter electrons undergo much more deflection than the protons