The Development of Modeling Atoms

Atomic Theories Before Dalton: Ancient India from 600BC

Period: Jan 1, 600 to Mar 1, 1807

There were numerous schools of "atomism" in ancient india that all taught theories and "known" facts about the atom. Later these schools developed theories that you could combine atoms to create more complex structures.

Dalton's Model of the Atom

Jan 1, 1808

He imagined the atom as a solid ball that was even throughout.
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His other beliefs were that all mater is composed of atoms, atoms cannot be made or destroyed, different elements have different types of atoms, chemical reactions occur when atoms are rearanged, and that compounds are formed from the same atoms that form the contituent elements.

Kelvin's Model of the Atom

Mar 1, 1867

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He believed that atoms were made up of unalterable vortices that endlesly flowed around in a fluid that he called the 'ether'. He also believed that each sub-atomic particle was more or less radioactive and that the arrangement of the electrons, protons, and nutrons effecte the radioactivity of the atom.

Thomson's Model of the Atom

Jan 1, 1897

Thomson discovered the electron through a number of expiriments, the most widely known being the cathode ray tube expiriment. Due to this discovery, he had a similar model to Dalton. The difference was that his model had electron's scattered through it. This model changed how scientists viewed the atom from then on, rather than a simple solid ball. He also believed that electrons were negetively charged and that the atom was positively charged.

Nagaoka's Model of the Atom

Jan 1, 1904

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Nagaoka's model of the atom was inspired by Saturn's rings. He invisioned a positively charged nucleus(the equivilent of Saturn) with negetively charged electrons revolving around the atom in a pattern similar to Saturn's rings.

Rutherford's Model of the Atom

Jan 1, 1911

Rutherford believed that the atom is mainly composed of empty space, and that electrons orbit randomly around the positively charged nucleus. Though in an expiriment involving shooting alpha particles at a thin sheet of gold. Due to the result of his expiriment, he concluded that Nagaoka's model of the atom was more acurrate.
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Bohr's Model of the Atom

Jan 1, 1913

Bohr believed that electrons orbited the nucleus in the atom in specific "shells". He believed that atoms generated or absorbed energy when electrons moved from one "shell" to another. This allowed Bohr to calculate the radius of a hydrogen atom, which is 145,000 times the size of the hydrogen atom's nucleus.

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Schrodinger's Model of the Atom

Jan 1, 1929

Alber Einstien proposed that Planck's quantum theory implied that electrons were both particle- and wave-like. This idea influenced Schrodinger's theory of wave mechanics. The wave mechanics predicted that the probability density of the electron in a hydrogen atom was greatest on the surface of the sphere.
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Chadwick's Model of the Atom

Jan 1, 1932

Chadwick's main discovery was the existence of nuetrons, the third known sub-atomic particle. This discovery explained two phenomena. How an atom's total mass is greater than the mass of it's combined electrons and protons. And how protons are able to stay so close together in dense clumps when their mutual positive charges should push them away.
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The Present Modern Model of the Atom

Mar 1, 2012

The present modern model of the atom has been recieving work from the 1920's to the present. In this model, negetively charged electrons from a cloud around the positively charged nucleus. It states that it is imposible to know where an elecrton is a any given moment.
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