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Aristotle
In 384-322 BC, Aristotle’s theory of elements was the most popular. Democritus’ theory of elements was the rivalling theory at the time but was soon stumped by Aristotles. Aristotle believed that all things are made of atoms and that all matter can be divided an infinite number of times, meaning, it is not possible to have a piece of matter that cannot be further divided. He suggested that everything was made up of some combination of the four elements (earth, fire, water and air). He also beli -
Isaac Newton
In 1704, Isaac Newton formulated a theory of light and proposed that the universe is a mechanical universe with small solid masses in constant motion. Newton’s contribution to our understanding of the atom was that atoms are held together with attractions, otherwise known as forces. He also stated that "matter is formed of solid, massy impenetrable particles”. -
John Dalton
In the early 19th century, John Dalton stated that matter is made up of indivisible atoms; that all atoms of a specific element are identical; that different elements have different atoms (size, shape, etc); that atoms cannot be created or destroyed; and that a chemical compound is composed of molecules, which are made of a small, fixed number of atoms from each element in the compound. -
Joseph John Thomson
J.J Thomson’s atomic theory brought forward the idea that electrons inside an atom were not invisible. He suggested that the atom could be a sphere model that had positively charged matter and negatively charged electrons. He discovered that electrons and protons were subatomic particles and suggested that protons were embedded in atoms and electrons are present in atoms, also known as the ‘plum pudding model’ -
Max Planck
Max Planck did work on thermodynamics which led him to the ‘quantum theory’ which explains the construct of energy states in atoms. He brought about the idea that energy is emitted in discrete quanta, different to what other theories had originally said. -
Ernest Rutherford
Ernest Rutherford conducted an experiment with a thin sheet of gold leaf, where alpha particles were fired at it to test the outcome. What was discovered was that a positively charged proton would meet with a positively charged nucleus and rebound from the charges repelling. To this, Rutherford suggested that the nucleus was surrounded by a large space before hitting the group of electrons that revolved around the nucleus of the atom. -
Niels Bohr
Niels Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in physics in 1922. He introduced the theory of electrons travelling in orbits around the atoms nucleus, the chemical properties of each elements being largely determined by the number of electrons in the outer orbits of its atoms. Niels Bohr also introduced the idea that an electron could drop from a higher-energy orbit to a lower o -
James Chadwick
James Chadwick was awarded the Nobel Prize for his discovery of the neutron. James Chadwick’s discovery made it possible to create elements heavier than uranium in the laboratory. His discovery particularly inspired Enrico Fermi, Italian physicist and Nobel laureate, to discover nuclear reactions brought by slowed neutrons, and led Otto Hahn and Fritz Strassmann, German radio chemists in Berlin, to the revolutionary discovery of “nuclear fission”. -
Higgs Boson - Peter Higgs
The Higgs boson is named for Peter Higgs who, along with two other teams, proposed the mechanism that suggested such a particle in 1964 and was the only one to explicitly predict the massive particle and identify some of its theoretical properties. The Higgs boson existence would have profound importance in particle physics because it would prove why some particles have mass and why others such a photons of light do not.
