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Democritus 400 BC
Democritus stated that all matter is made up of atoms.
He also stated that atoms are eternal and invisible and so small that they can’t be divided, and they entirely fill up the space they’re in.
400 BC Scientific Contribution
Democritus was believed to have excelled in all branches of knowledge, most notably philosophy and science. His name is most widely associated with the foundlings of the atomic theory of matter, according to which all matter is composed of single, indivisible atoms. -
Antoine Lavoisier Atomic Model
The law of conservation of mass states that the total mass present before a chemical reaction is the same as the total mass present after the chemical reaction; in other words, mass is conserved. The law of conservation of mass was formulated by Antoine Lavoisier Scientific Contribution
Antoine-Laurent de Lavoisier is one of the most important scientists in the history of chemistry. He discovered elements, formulated a basic law of chemistry and helped create the metric system. -
John Dalton
John Dalton, a British chemist and physicist, developed a theory that matter is simply composed of atoms of different weights and is combined in ratios by weight.
Also proposed that these atoms are spherical, and are in motion.
Scientific Contribution
In 1801, he came up with the ‘Dalton Law’ also known as Dalton's Law of Partial Pressures’. This theory is used by scuba divers today to gauge pressure levels at different depths of the ocean and its effect on air and nitrogen levels. -
Proust's Atomic Theory
The law of definite proportions, sometimes called Proust's Law, states that a chemical compound always contains exactly the same proportion of elements by mass.
An equivalent statement is the law of constant composition, which states that all samples of a given chemical compound have the same elemental composition by mass.
Scientific Contribution
Proust, Joseph Louis was a French chemist who became known for helping prove the idea that every pure chemical compound consists of elements in a de -
JJ Thomson Atomic theory
The Plum Pudding Model is an atom model proposed by JJ Thomson, the physicist who discovered the electron.
In this model, the atom was imagined to be a sphere of positive charge with negatively charged electrons dotted around inside it like plums in a pudding.
Scientific Contribution
The early theoretical work of Thomson broadened the electromagnetic theories of James Clerk Maxwell’s, which revolutionized the study of gaseous conductors of electricity, as well as the nature of cathode rays. -
Ernest Rutherford Atomic Theory
Rutherford atomic 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.
Scientific Contribution
The British physicist and chemist, Ernest Rutherford is known for his r -
Neils Bohr Atomic Theory
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.
Scientific Contribution
Bohr’s model of atomic structure was published which became the basis of -
James Chadwick Atomic Theory
James Chadwick discovered a new type of radiation that consisted of neutral particles. It was discovered that these neutral atoms come from the nucleus of the atom. This last discovery completed the atomic model. Scientific Contribution James Chadwick discovered the neutron in 1932. Neutrons could be used to split heavy atoms apart atomic fission producing a large amount of energy, which could be used in atomic bombs or nuclear power plants.
