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Democritus Model
In the days before electricity, the internet, cable TV and cell phones, people actually spent a lot of time thinking and philosophizing about the world around them (it's true - I was there!). While the "ancients" believed everything was made up of either earth, wind, fire, or water, Democritus had other ideas. He believed - after hearing a guy named Leucippus chat - that there had to be a basic building block that made up all other matter. Common (and useful) analogy is to think of a big toy ca -
Dalton Model
Notice the big old gap between the time when Democritus first shouted, "Atomos! We've got atomos here!" to the publication of Dalton's more formal theory? Told you Aristotle threw us back into the atomic dark ages a bit. It's not that nobody was thinking about atoms at all for nearly 2000 years (check out that expanded timeline), but what Dalton discovered and what he formally published about atoms earns him the next slot on our field trip through the history of atomic models. -
Thomson Model
earliest theoretical description of the inner structure of atoms, proposed about 1900 by Lord Kelvin and strongly supported by Sir Joseph John Thomson, who had discovered (1897) the electron, a negatively charged part of every atom. Though several alternative models were advanced in the 1900s by Lord Kelvin and others, Thomson held that atoms are uniform spheres of positively charged matter in which electrons are embedded. Popularly known as the plum-pudding model, it had to be abandoned (1911) -
Rutherford Model
description of the structure of atoms proposed (1911) by the New Zealand-born physicist Ernest Rutherford. The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun. The Rutherford atomic model has been alternatively called the nuclear atom, or the planetary model of the atom. -
Bohr Model
In 1913 Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus. The motion of the electrons in the Rutherford model was unstable because, according to classical mechanics and electromagnetic theory, any charged particle moving on a curved path emits electromagnetic radiation; thus, the electrons would lose energy and spiral into the nucleus. To remedy the stability problem, Bohr modified the Rutherford model by requiring that the el -
Electron cloud model
Erwin Schrödinger built upon the thoughts of Bohr yet took them in a new direction. He developed the probability function for the Hydrogen atom (and a few others). The probability function basically describes a cloud-like region where the electron is likely to be found. It can not say with any certainty, where the electron actually is at any point in time, yet can describe where it ought to be. Clarity through fuzziness, is one way to describe the idea. The model based on this probability
