atomic theory

By Jayhawkmelody@yahoo.com
  • 440

    Democritus BCE

    Greek philosipher Democritus has a theory that at the base of everything on Earth is a small particle that can not be divided. He called this particle atomus (atom) which means indivisible.

  • Dalton (British chemist and school teacher)

    Developed a theory that states
    all substances are made of atoms.Atoms are very small particles that can't be created, divided, and destroyed.
    Atoms of the same element are exactly alike , and atoms of different elements are different.
    Atoms join with other atoms to make new substances.

  • Tomson (British scientists)

    Tomson proved a mistake in Dalton's theory. He found small particles inside the atoms, this means that atoms can be divided. He experimented with a cathrode-ray tube. A positively charged plate attacked the tube. He concluded that the beam was made of negative electric charges, negatively charged particles are present in every kind of atom. negative particles are called electrons. Plum pudding model- he thouht that electrons were mixed throughout an atom, like plums in a pudding.

  • Rutherford (student of tomson)

    Designed an experiment to study the parts of an atom.
    He aimed a beam of small,positivley charged particles at a thin sheet of gold foil. he put a special coating behind the foil.
    The coating glowed when hit by the positivley charged particles.
    He thought atoms were soft "blobs", Rutherford expected the particles to pass right through the gold in a straight line. Most of them did just that, but some of the particles were deflected.

  • Rutherford changed his theory

    Rutherford was forced to discard the Plum Pudding model.He then developed the planetary model of the atom which put all the protons in the nucleus and the electrons orbited around the nucleus like planets around the sun.

  • Bohr improves the atomic theory

    developed the Bohr atomic model, with electrons travelling in orbits around the nucleus, and chemical properties being determined by how many electrons are in the outer orbits. He also supported the Planck quantum theory, stating that when electrons change orbits they emit a quantum of discrete energy.

  • Shrodinger's theory

    Shrodinger described how electrons move in wave form, and developed the Schrodinger equation.It describes how the quantum state of a system can change with time.