-
400 BCE
Democritus/ Dalton's Model
Democritus is a Greek Philosopher who developed the concept of atoms and believes that everything is composed of atoms.
Dalton is a Chemist who discovered a method for measuring the masses of the elements in a compound. He had the idea that atoms were invisible. -
Thomson's Model
He experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Cathode has a negative charge. Anode has a positive charge.
His model is called "plum pudding" because it reminded scientists of raisons which then reminded them of plums. The earliest theoretical description of the inner structure of atoms, proposed about 1900 by William Thomson. Sir Joseph John Thomson discovered the electron. -
Rutherford's Model
Rutherford was a physicist. The atom contains a central part called nucleus which is surrounded by electrons. The nucleus of an atom is positively charged. The size of the nucleus is very small as compared to the atomic size. Rutherford's gold foil experiment showed that the atom is mostly empty space with a tiny, dense, positively-charged nucleus. Based on these results, Rutherford proposed the nuclear model of the atom. -
Bohr’s Model
Bhor was a philosopher and a promoter of scientific research. He proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level to another. Of the hydrogen atom is based on three postulates: (1) an electron moves around the nucleus in a circular orbit, (2) an electron's angular momentum in the orbit is quantized, and (3) the change in an electron's energy. -
Quantum Mechanical Model
This model uses complex shapes of orbitals, volumes of space in which there is likely to be an electron. So, this model is based on probability rather than certainty. Erwin Schrödinger invented this. Erwin was an Austrian theoretical physicist.
