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400 BCE
Democritus formulates his atomic theory
An ancient Greek philosopher who is viewed by many as being the “father of modern science”.
This is due to his theory of universe that is made up of tiny “atoms”, which he described as "that which cannot be divided any further"
But he does not have a "specific" model of the atom. This model is wrong because he did not describe the electrons and protons that we now know they have, but since he didn't have the resources to observe, it's what he could do. -
Dalton's atomic model
He proposed that all matter is composed of very small things called atoms, and he described the atom as a sphere with a positive charge. His theory led to the creation of others, changing science forever. This model is wrong because electrons are not included, with their respective orbits, but they have not been discovered yet. -
Thomson's atomic model
In 1897, J. J. Thomson discovered the electron, which led him to propose his atomic model in 1904, which consisted of mutiple electrons inside a positive sphere, sort of like a plum pudding, the electrons being the plums and the positive sphere being the pudding. This model is wrong because he theorized that all of the components of the atoms composed one sphere, positive and negative. -
Ernest Rutherford makes his own model
In 1911, Rutherford formulated his atomic theory by analyzing that Thomson's model was incorrect, and he did an experiment in which he blasted a very thin gold foil with alpha particles, and from his observations, formulated his own model, in which electrons orbit a positively charged nucleus. This model is wrong because he did not depict specific orbits for the electrons, which Neils Bohr led to realize that the electron will loose energy over time and collapse into the nucleus. -
Neils Bohr does corrections to Rutherford's model and makes his own
In 1913, Neils Bohr after analyzing Rutherford's model, formulated that the electrons will orbit the nucleus until they ran out of energy and collapse into the nucleus, which made the atoms very unstable, but atoms are stable, so he proposed that the electrons orbit in arranged orbits, in which they go to an upper orbit when they absorb energy, and go to a lower orbit when it radiates energy. This model is technically not wrong, but it assumes an electrons location without calculations. -
Erwin Schrodinger makes his atomic model
In 1926, Erwin Schrodinger proposed the quantum-mechanical model, in which he took Bohr's model a little further. This model does not depict a specific place in which an electron is located, but it makes an estimation on where the electron is located and in which areas there is more probability of finding an electron. This is the model which is used today. This model depicts in a good way the structure of atoms and the location of electrons orbiting the atom. We might update it in the future. -
Bibliography
Matt Williams. (11/12/15). Who Was Democritus?. 5/3/19, de UNIVERSE TODAY Sitio web: https://www.universetoday.com/60058/democritus-atom/
Matt Williams. (1/12/14). What Is John Daltons Atomic Model?. 5/3/19, de Universe Today Sitio web: https://www.universetoday.com/38169/john-daltons-atomic-model/
