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Discovered Year

400 B.C.E

Atomic Model Name

The Sphere Model

Conclusion

Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped. Differences in atomic shape and size determined the various properties of matter.

Pros

First proposed atoms

Unique atoms for each element

Cons

Macro properties

Too many elements

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Discovered Year

1803

Atomic Model Name

The Billiard Ball Model

Conclusion

John Dalton concludes from his experiment with different gases under controlled conditions. With the observations he made in his experiment, he brought back the geek philosopher’s idea of the atom, based on the results of his experiment he claims on what think it’s true on the atomic theory. Dalton stated that all, all matter is composed of small, indivisible particles called atoms., All atoms of a given element are identical in mass and properties., Atoms are not created, destroyed, or converted into other kinds of atoms during chemical reactions; they are simply rearranged into new compounds. Last compounds are formed by a combination of two or more atoms in definite arrangements in the ratio of small whole numbers. Dalton’s experimentation supported the law of conservation, just like the idea that different elements are made up of different size particles.

Pros

John Dalton of his atomic theory is that it introduces the idea of each element having a characteristic atomic mass, it was an important step towards the classification of the elements for the periodic table. It also helps to learn that atoms are combine it creates to form a compound.

Cons

John Dalton of his atomic theory is that some of his theories are no longer valid. Another disadvantage of his theory is that it doesn’t explain how atoms of different elements from each other. It failed to explain how different atoms hold together in a molecule.

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Discovered Year

1897

Conclusion

J.J Thompson discovered that all atoms contain tiny negative charge particles called electrons spread around a positive charge

Pros

Discovered electrons

Cons

The experiment of Thompson failed to explain how the positive charge holds the electrons inside of the atom.

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Discovered Year

1911

Atomic Model Name

Rutherford Planetary Mode

Conclusion

The conclusion from Ernest Rutherford was that atoms are mostly made up of empty space. He also concluded that the atom has a positive charge in the nucleus and is surrounded by negative particles called electrons. The final thing he concluded was that the mass of the atom is located in the middle, with both protons and neutrons.

Pros

This model was able to explain the gold foil experiment, and concluded that the Thomson model was incorrect

Cons

The model couldn’t prove the fact that electrons just don’t float around but actually go along a circular path

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Discovered Year

1913

Atomic Model Name

Planetary model​

Conclusion

Science is called the body of knowledge about our physical world acquired through observation and experimentation. The scientific method defines the process of generating explanations and predictions that can be validated and reflected through observations, measurements and interpretation of data. Scientific hypotheses can be created and accepted, but they can later be proven false.​

Bohr's conclusion According to Bohr's third postulate, electrons only emit or absorb energy when they jump from one orbit to another. As long as the electron remains in the same orbit, its energy will be constant. The energy levels correspond to the shells of the atoms of the elements in which the electrons are found.​

Pros

With this theory, Bohr was able not only to determine the energies of the electrons in their orbits, but also to broadly explain the visible spectral series of hydrogen, with astonishing precision.​

Cons

He could not explain the details of the Hydrogen and Helium atomic spectrum.​

He did not explain the splitting of spectral lines in presence of a magnetic field.​

The intensity of spectral lines was not explained by him.

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Discovered Year

1926

Atomic Model Name

Quantum Mechanical Model

Conclusion

Erwin Schrödinger has discovered the waves mechanics of an electron. Erwin Schrödinger said that all electros travel in waves their movement in never determined on where they are. Erwin Schrödinger has created the quantum mechanics using the quantum mechanics has help determine where could electrons be in the electron cloud

Pros

Erwin Schrödinger mathematical equation has help determine where could electrons be at the same time gather more information about electrons

Cons

Erwin Schrödinger equation has help a lot but at the same time using that equation has had some trouble on actual determining an actual solution of numbers

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Discovered Year

1932

Atomic Model Name

Rutherford-Bohr atomic model

Conclusion

James Chadwick has discovered the neutrons. James Chadwick discovered the neutron by doing a experiment that consisted of him using alpha particles putting it to beryllium showing an unexpected effect of radiation.

Pros

Prove existence of the nucleus

Cons

The atom mass was greater than the protons and electrons