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442 BCE
Democritus Atomic 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.
He knew that if you took a stone and cut it in half, each half had the same properties as the original stone. So if you continue cutting there would be a tiny particle that can't longer be divided, he open the study of the atom.
It was wrong since there are more particles in the atom than just a electrically charge particle. -
John Dalton "Billiard Ball Model"
He came up with a theory on the smallest particles in the universe, of what makes up what we call "matter". All matter consists of indivisible particles. He gave 4 postulates like all elements are composed of atoms and different elements got different atom, all same elements got the same atom, and different atoms combine to make a compound (atoms have to be in definites whole number ratios).
This theory was wrong because his theory needs of the sub-atomic particles, he deduced a ball of energy. -
JJ Thomson "Plum-Pudding Model"
JJ Thomson didn't believe that atom was indivisible, he was experimenting with cathode ray tubes, he saw the glowing stream and theorized that the stream was made up of negative charge particles (electrons). He told that the Atom may be like a plum pudding with a positively charged particle as the nucleus and the electrons were scattered in the proton.
He help discovering the electrons.
This model was wrong because he didn't know about the existence of another sub-particle, the neutron. -
Rutherford "Planetary Model"
Rutherford proposed that atoms consist of protons in a nucleus but there were electrons rotating around the nucleus, they were held with the attraction between protons and neutrons.
His theory was made when he deduced that some alpha particle would trespass a gold foil, but instead of completely trespassing, some alpha rays bounced, making him deduced that there were hollow places.
The theory was wrong because when the particles lose energy and the force is annulated and they stop moving. -
Bohr "Energy Level Model"
Bohr stated that the atom has orbits (K, L, M, N). They were at distance with the nucleus, also they became larger, the further away they are from the nucleus and orbit has more energy than the others. He also stated: an electron can jump from one to another level (if it jumps it uses energy, going backward they gain it).
This model was based on his observations of the atomic emissions spectrum of the hydrogen atom (each color corresponding to a level of energy).
This goes for the hydrogen atom. -
Schrodinger "Quantum Mechanical Model"
Is based in quantum theory, which says matter also has properties associated with waves.
This used complex shapes for the orbitals, now called clouds, Schrodinger discovered that the molecules moves and nd they have no exact location, but were the cloud is more dense, more probability of an electron would be there this is known as the Uncertainty Principle.
This model introduce the sub-energy levels (s, p, d, f).
This is the most accurate atomic model until the day.
