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500 BCE
The Alchemist Atomic model
Alchymist Atomic model -
500 BCE
Main contribution
Develop the theory—that all metals are composed of mercury and sulfur and that it is possible to change base metals into gold. -
500 BCE
Description model
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500 BCE
How was the model wrong?
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400 BCE
Main contribution
Democritus greatest contribution to modern science was arguably the atomic theory he elucidated. -
400 BCE
How was the model wrong?
Democritus called these infinitesimally small pieces of matter atomos, meaning "indivisible." He suggested that atomos were eternal and could not be destroyed. -
400 BCE
Democritus Atomic model
Democritus' Atom -
400 BCE
Description model
Democritus’s model stated that matter consists of invisible particles called atoms and a void (empty space). He stated that atoms are indestructible and unchangeable. -
John Dalton Atomic Model
Dalton's Model of an Atom -
Description model
Dalton's atomic theory proposed that all matter was composed of atoms, indivisible and indestructible building blocks. While all atoms of an element were identical, different elements had atoms of differing size and mass. -
Main contribution
John Dalton's theory was to show that he could tell an atom just by its weight. The modern atomic theory shows how atoms are more complicated than hydrogen. -
How was the model wrong?
An atom can be further subdivided into protons, neutrons and electrons. However an atom is the smallest particle that takes part in chemical reactions. According to Dalton, the atoms of same element are similar in all respects. These atoms are known as isobars. -
Joseph Thompson Atomic Model
Plump pudding model -
Description model
In this model the atom was also sometimes described to have a “cloud” of positive charge. -
How was the model wrong?
The atom contains a small, massive, positively charged nucleus. He also agreed with Nagaoka that the electrons move in circular orbits outside the nucleus. -
Main contribution
Thomson realized that the accepted model of an atom did not account for negatively or positively charged particles. -
Rutherford Atomic model
Nuclear model -
Description model
Rutherford's model shows that an atom is mostly empty space, with electrons orbiting a fixed, positively charged nucleus in set, predictable paths. -
Main contribution
With his well-known gold foil experiment in which he demonstrated that the atom has a tiny and heavy nucleus. -
How was the model wrong?
The main problem with Rutherford's model was that he couldn't explain why negatively charged electrons remain in orbit when they should instantly fall into the positively charged nucleus. -
Niels Bohr Atomic model
Rutherford-Bohr Model -
Main contribution
Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. -
Description model
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How was the model wrong?
Bohr's model is that it works very well for atoms with only one electron, like H or He+, but not at all for multi-electron atoms. -
Schrödinger Atomic Model
Quantum mechanical model, proposed the model in which
electrons are treated as waves. -
Description model
A powerful model of the atom was developed by Erwin Schrödinger in 1926. ... The Schrödinger model assumes that the electron is a wave and tries to describe the regions in space, or orbitals, where electrons are most likely to be found. -
Main contribution
Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom. -
How was the model wrong?
It assumed that the electron is a wave and tries to describe the regions in space, or orbitals, where electrons are most likely to be found.
