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400 BCE
Democritu´s model
stated that matter consists of invisible particles called atoms and a void (empty space). He stated that atoms are indestructible and unchangeable. Also that they are homogenous, meaning they have no internal structure. His atomic model was solid, and stated all atoms differ in size, shape, mass, position and arrangement, with a void exists between them.
It was wrong because the atoms don´t differ in shape and dont differ in size if they are from the same element -
Dalton´s Atomic model
1.All elements have atoms. cant be divided
2.Atoms of same element are alike
3.from diff elements are diff
4.atoms of diff elements combine to form a compound
5.chemical reactions occur when atoms are separated, joined or rearranged
The indivisibility of an atom was proven wrong. However an atom is the smallest particle that takes part in chemical reactions -
Thomson's Plum pudding model
each atom was a sphere filled with a positively charged fluid, known as the “pudding”. Scattered in this fluid were negatively charged electrons, these were the “plums” in the pudding. Thomson suggested that the positive fluid held the negatively charged electrons in the atom because of its electrical forces.
J.J. Thomson was "wrong" because he assumed that the positive charge of an atom was all one uniform blob of matter with the electrons moving in orbits inside the nucleus. -
Rutherford's Planetary Model
Rutherford proposed that atoms consisted of a small dense center filled with positive charges. He named this center the nucleus. He then said that negatively charged electrons were scattered surrounding this dense, positively charged center. He stated these negatively charged electrons were held in orbit by the positively charged nucleus, due to the electrical forces. Rutherford's Model doesn't make sense in terms of conservation of energy. -
Bohr's energy level model
Electrons move in fixed energy levels around the nucleus, these called electron shells. They became larger the further away they are from the nucleus, and electrons furthest from the nucleus have higher energy. An electron can jump from a lower orbit to a higher orbit by absorbing energy. These electrons then lose energy when they are allowed to cool, giving them emission spectra for all different elements.
Bohr's model breaks down when applied to multi-electron atoms. -
Schrödinger's Quantum Mechanical Model
This model does not define the exact path of an electron, but rather, predicts the odds of the location of the electron. This model can be portrayed as a nucleus surrounded by an electron cloud. Where the cloud is most dense, the probability of finding the electron is greatest. This model introduced the concept of sub-energy levels.
