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400 BCE
Democritus atomic model
Democritus stated that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through space until stopped. Differences in atomic shape and size determined the various properties of matter. The main contribution of this model is that was the first time that the concept of ''atom'' was used to explain the matter. Finally, the model was wrong in saying that atoms were indivisible. -
1 BCE
Atomic models
In this timeline, all the atomic models are going to be explained, also the contribution to today's understanding of the atom. And how the model was wrong. -
John Dalton atomic model
His theory stated that atoms are indivisible, those of a given element are identical, and compounds are combinations of different types of atoms. This model contributes in recognizing atoms of a particular element differ from other elements. And the model was wrong in saying that atoms were indivisible. -
J.J Thomson atomic model
He discovered the atoms, and also he produced the ''plum pudding'' model of the atom. It shows the atom as composed of electrons scattered throughout a spherical cloud of positive charge. This model contributed to recognizing electrons as components of atoms. The model was wrong in saying that there were no nucleus. -
Ernest Rutherford atomic model
Rutherford fired positively charged Alpha particles at a thin sheet of gold foil. Most passed through with little deflection, but some deflected at large angles. This was only possible if the atom was mostly empty space. This model contributed to realizing positive charge was localized in the nucleus of an atom. The model was wrong in not explaining why electrons remain in orbit around the nucleus. -
Niels Bohr atomic model
Bohr modified Rutherford’s model of the atom by stating that electrons moved around the nucleus in orbits of fixed sizes and energies. Electron energy in this model was quantized; electrons could not occupy values of energy between the fixed energy levels. The model contributed in proposing stable electron orbits explaining the emission spectra of some elements. Nevertheless, this model did not work well with heavier atoms -
Erwin Schrödinger atomic model
He stated that electrons do not move in set paths around the nucleus, but in waves. It is impossible to know the exact location of the electrons. Instead, we have ‘’clouds of probability’’, called orbitals, in which we are more likely to find an electron. This model contributed in showing electrons do not move around the nucleus in orbits, but in clouds where the position is uncertain. Finally, it is still widely accepted as the most accurate model of the atom, so, there are no mistakes.