A1

ATOMIC THEORIES.

  • Democritus. 400BC
    400

    Democritus. 400BC

    All things are composed of invisible tiny particles of matter, which can’t be destroyed.
  • John Dalton

    John Dalton

    · Described tiny indivisible particles called atoms.
    · Atoms can’t be divided or destroyed.
    · Atoms can join together to form molecules.
    · Atoms of one element are all the same.
  • J.J. Thompson

    J.J. Thompson

    · Atoms contain electrons, which have a negative charge.
    · Atoms are solid with electrons and protons randomly placed through them.
  • Ernest Rutherford

    Ernest Rutherford

    · Atoms have a dense nucleus which contains protons, and most of the rest is empty space.
    · Electrons orbit around the nucleus like planets around the sun.
  • Niels Bohr

    Niels Bohr

    · Electrons are arranged in layers or shells around the nucleus.
    · The shells have different energy levels, and electrons fill up the lowest levels first.
  • James Chadwick

    James Chadwick

    · The nucleus also contains neutrons, which are unchanged particles with a similar mass to protons.