1 This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. John Dalton’s contribution was that he reintroduced the idea of particles, which vary in shape and size based on the substance type and the mass and volume of this substance. In atomic theory and quantum mechanics, an atomic orbital ( / rbtl /) is a function describing the location and wave-like behavior of an electron in an atom. 500 BCE- AlchemistsĪlchemists developed the idea that all metals are composed of mercury & sulfur and that changing base metals into gold is possible. Although two centuries old, Daltons atomic theory remains valid in modern chemical thought. Atomic Theory to the 19th century: The earliest known examples of atomic theory come from ancient Greece and India, where philosophers such as Democritus postulated that all matter was composed of. And most scientists believed him over Democritus. 440 BCE- AristotleĪristotle’s contribution was completely different he disagreed with Democritus and stated that particles comprise the four elements instead.

He also said that they were invisible physically but not geometrically. He proposed that the entire world was made up of tiny particles surrounded by an empty space. 440 BCE- Democritusĭemocritus’s theory was the first theory to be contributed to the atomic theory. In his beliefs air, fire, water, earth mingle and separate under the compulsion of love and strife. Empedocles was responsible for separating air as a separate substance.

When was the atomic theory discovered