-
700 BCE
Asharya Kanada
The Hindu philosopher first conceptualized the idea of the atom. The idea came to him while he was eating food. He broke his food into small pieces until he was no longer able to do so. While it is bad manners to play with your food, he is remembered fondly by humanity for doing so. He theorized that tiny, undivideable and indestructible particles must exist, and that the Earth was made up of many such particles. He named it 'anu', and it is known as the atom. -
450 BCE
Empedocles
He believed that the Earth was made of 4 elements, earth, wind, fire, and water. The thought process that every creation on Earth could be explained by a finite number of elements was a novel concept, and one scientists have made great strides with in this age, with more knowledge and technology. His concept is cemented in the axioms of atomic theory. -
420 BCE
Democritus
He conceptualized geometric, indivisible particles, and said that everything in the world is made up of them. He came up with this independent of Kanada. Unlike Kanada, he also theorized that these atoms contained different properties and were bonded in different ways. -
John Dalton
John Dalton modernized and updated the atomic theory of Democritus. He stated that atoms are building blocks of chemical structures and that these atoms can be combined into compounds to form a more complex structure. Through rigorous experiments and tests, he realized his theory. -
J.J Thomson
He discovered the electron, which he called cathode ray particles. He explored their properties to the best of his ability, finding out that they are negative and had minimal mass. Since he knew atoms were overall neutral, he hypothesized something commonly known as the 'plum pudding' model. He represented electrons as negative, and protons as positive, which made a neutral atom. -
Marie Curie
She invented the field of study of atom physics. She was a scientist who was studying uranium rays, and theorized that the rays from radioactive elements were not dependent on the form of the element, rather its atomic structure. The activity of rays emitted was dependent on atomic structure and number of atoms. -
Nagaoka Hantaro
Hantaro developed the "Saturnian" model. He postulated that the atom was inherently unstable as the electron would gradually lose energy and fall into the nucleus by constantly radiating. He theorized the fact that the atom has a very large atomic nucleus, and that electrons travel around the center of the atomic nucleus by electrostatic forces. -
Albert Einstein
Einstein, while mainly known for his achievments in mathamatics and physics, also had a huge contribution in the atomic theory of matter. He mathematically proved the existence of atoms, which led into the general theory of relativity. -
Max Planck
Max Planck did not directly affect the atomic theory of matter, his research helped scientists like Bohr expand the atomic theory. He explained that the reason objects glow when they are heated is because of quanta. A term he coined for energy that is radiated in small amounts. Quanta explains the spectrum radiation that causes the objects to glow. -
Lise Meitner
She was a nuclear physicist who discovered radioactive recoils and their capacity to produce very pure elements. She found that a nucleus recoils after emitting an alpha particle, and can attract to a negatively charged particle while it is recoiling. By recoiling elements onto the negatively charged particle, one can collect pure elements. -
Ernest Rutherford
He created the nuclear model of the atom. He created the gold foil experiment, where alpha particles were shot at a thin sheet of gold. He noticed that most got through, but some bounced back, and theorized that those that bounced his the nucleus, and that those that went through must have been passing through empty space. From this he postulated a theory where the centre of the atom was the positive nucleus, around it were tiny negative electrons, and empty space in between. -
Niels Bohr
Using quantum theory, Bohr explained why atoms emit light in fixed wavelengths. He theorized that electrons move around the nucleus only in prescribed orbits. He displayed this with his model of the atom. -
Louis de Broglie
Louis de Broglie conducted multiple experiments. Through these experiments, he theorized that electrons must contain restrictions on their motion. He conceptualized waves and claimed that waves had properties and boundaries that restricted the motion of electrons. -
Wolfgang Pauli
He came up with two new and different numbers. These integers formulated the Pauli principle. This principle states that no two electrons could have the same sets of quantum numbers. This principle also applies to protons and neutrons. -
Erwin Schrodinger
Schrodinger came up with the electron cloud model. This model goes against the theory that electrons move in an orbit motion around the nucleus. He came up with a mathematical equation that informed scientists about the approximate location of the electron. This is similar to a cloud in the way that the location of the electron would be in a general cloud of space. -
Werner Heisenberg
Heisenberg created the uncertainty principle. He discovered that we can only know either the displacement (position) of a particle, or its momentum. We cannot know both simulataneuosly. -
James Chadwick
He found the location of the subatomic particles called neutrons in atoms using a neutron chamber. Neutrons are located in the middle of an atom, along with the protons, in the nucleus. Neutrons contribute to the same effect of a proton to atomic weight, but are not charged. -
Peter Higgs
A physicist who theorized that a Higgs Boson creates a Higgs Field from which all mass is attained and leads to the creation of quarks. His work was not considered to be true until very recently. -
Murray Gell-Mann
He claimed that protons and neutrons are were made up of smaller building blocks, and named these building blocks quarks. He took pairs of atoms and smashed them together to try and break them down to reveal these smaller building blocks. He discovered that subatomic particles are made of quarks. -
Richard Bader
He discovered that the density of an electron was crucial to understanding the behavior of atoms in molecules. He also claimed that there were no orbitals or shells in the molecules. His ideologies were shunned as it went against many theories that were already accepted. -
Ronald Gillespie
He created the valence shell electron repulsion theory. It is used in advanced chemistry to determine the future shape of an atom based on the number of electron pairs outside the nucleus in the outermost shell.
