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The Atom is established as a part of Science
(1803) John Dalton established the atom as a part of science. He introduced the concept that elements differed due to the mass of their atoms, and that all matter was composed of indestructible building blocks, and that different elements had different atoms of different size/mass. Dalton also suggested that chemical reactions were the rearrangement of atoms, and compounds were made of a defined ratio of atoms. Later on, this established the basis of understanding radioactivity. -
The "Plum Pudding" Atomic model was made
(1897) JJ Thomson discovered the electron, interpreted by the deflection on negative rays sent through atoms. He then created the “Plum Pudding” atomic theory, which negative electrons were inside a positive charge, hence the electrons being the “raisins” and the “dough” being the positive charge. -
Polonium and Radium discovered
Marie Curie discovered Polonium and Radium, and found that thorium-composed compounds gave of rays, similiar to uranium. -
Alpha and beta type radiation discovered.
(1898) Rutherford discovered that there were "alpha" and "beta" types of radiation, through studying the effects of radiation of uranium. Thorugh his discovery, we found out that they are not rays; they are particles emitted in attempt from the atom to stablise. -
Radioactive "half-life" concept is created
(1902) While working with Frederick Soddy, Ernest Ruthurford discovered "half-life" in radioactivity, the time taken of the decay of radioactive materials, in which the time for half of the radioactive nuclei to decay. -
Radioactivity
Although Henri Becquerel discovered radioactivity, Marie Curie who coined the term.Marie became the first woman to be awarded a nobel prize, and was awarded for discoveries in radioactivity, the study and discovery of various elements for radiation. Her research concluded that radioactivity depended on the atom itself, rather than how atoms were arranged in molecules. -
Radioactivity of potassium
(1905) Thomson discovered the natural radioactivity of potassium -
The Rutherford model is created
(1909) Ernest Rutherford discovered that atoms had some parts that were free, and some parts that were solid by firing atoms from gold foil, and found that the electrons widened as it passed through the gold foil. He then created the "Rutherford Atomic Model", where the electrons circled the nucleus. He also developed a way to describe and guage radioactivity. -
The Bohr Atomic Model is established
(1913) Neils Bohr’s contribution to the atomic structure by creating the Bohr model of the atom, which was that electrons had a certain amount of energy, and that they could jump from one shell to another. His theory meant that electrons had a stable orbit, much like the solar system. -
First evidence of stable isotopes
(1913) Thomson found the first evidence of a stable isotope, as part of his discovery into canal rays. -
Electromagnetic radiation discovered in atoms
Neils Bohr discovered that electromagnetic radiation was emitted when an electrons jumped from orbits, He concluded this from his own research. Although this was not strictly correct, it lead on to influence future discoveries in atomic theory. -
The Neutron was found
(1932) James Chadwick proved the existence of neutrons in atoms. He noticed that the atomic number was always less than the atomic mass, which led him to believe that there was something besides the protons in the neutrons were adding mass. His theory was that neutral parts in atoms were neutrons, and helped explain the structure of an atoms nucleus. -
The Atomic Theory was formed
(465 BC) Democritus was a philosopher famous for adopting the atomic theory from his mentor, Leucippus. The theory stated that “The universe is composed of two elements: the atoms and the void in which they exist and move.” The theory suggested that there were tiny particles of matter that made up everything in life. The theory ,at the time, stated that atoms make up all matter, and that they were all indestructible, solid and invisible, as well as differing in size, shape, mass and arrangement
