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Atom timeline by Vanessa Sifuentes

vanessa.sifuentesp

Created on March 4, 2021

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Transcript

THE ATOM

Through history

Based on his theory we can define the atom as the basic unit of an element that can be part of a chemical combination.

1803

His theory says that:- The elements are formed by very small particles called atoms - Compounds are made up of atoms with more than one chemical element - A chemical reaction includes only the union, separation or rearrange of the atoms, which can be neither created nor destroyed.

Jonh dalton atomic theory

His contributions were: - He discovered the existence of negative atoms while realizing an experiment with gases and named them electrons. - He concluded that the mass of the electron was only one two-thousandth of the mass of the atoms in the material. - Thompson suggested the first model of the atom, considering it as a compact, homogenous, indivisible spher with a positive charge in which the electrons were embedded as if they were raisings in a pudding.

1897

THOMSON MODEL OF THE ATOM

Contributions: - In 1909 he concluded by an experiment, that atoms were practically hollow and that they were not a positive homogenous mass - Concluded that if the atom had electrons, in order to neutralize the negative charge, positively charged particles had to exist in the same amount with a high concentration, which he called atomic nucleus. - In 1911 he made a new atomic model. In his model the atom has an nucleus and an outer region, 99.9% of the the mass is in the nucleus which is made up by protons, and in the outer region we can find the electrons revolving around the nucleus.

1909

1911

Rutherford discoveries and model

Bohr:- He taked in count the planetary model - Bohr corrected the flaws of Rutherford's model and explained why the atom did not collapse, and clarified the hydrogen emission spectrum. - His model says that: *Electrons describe circular orbits around the atomic nucleus without radiating energy. These orbits are named energy levels. * Electrons can only rotate around the nucleus. *Energy can be released or absorbed in the form of photons and corresponds to the energy diference between the levels.

1913

bohr atomic model

made by:Vanessa Sifuentes