Timeline of Atomic Theory

Acharya Kanad

600 BCE

Kanad was believed to be the first one to have an idea of indestructible particle of matter. This idea came to him when hes was walking around, breaking his food up into smaller pieces.

First idea of atoms

500 BCE

Leucippus and Democritus purposed to the early community of Greek chemists that matter was made up of different formations of invisible particles called "atomos" make up forms of matter.

Crazy Alchemists

500 BCE

The alchemists contributed to the atomic theory by helping us further develop the modern periodic table.

Robert Boyle's discussion

1661

Boyle presented a discussion of atoms in his 'The Skeptical Chemist'.

John Dalton's first modern Atomic Theory

1803

Dalton had presented the first modern atomic theory by developing the law of multiple proportions.

Thomson's discovery

1897

J.J. Thomson discovered that some of the invisible particles were negatively charged, which we would later call electrons.

Marie Curie

1898

Curie conducted several experiments on uranium rays and found they stay constant. She theorized that the rays had come from the elements atomic structure. This discovery would go on to be the first step in atomic physics. She also discovered two new elements, radium and polonium.

Max Planck

1900

Planck was the original creator of the quantum theory. He further developed an understanding of atomic and subatomic processes. He created a constant that helps us describe the behavior of particles and waves at an atomic level.

Hantaro Nagaoka

1904

Nagaoka proposed an alternative planetary atomic model. The positively charged nucleus is surrounded by rings of negatively charged electrons. Like Saturn's rings.

Einstein's Theory

1905

Albert Einstein is arguably the most famous physicist. He was responsible for creating the theory of relativity, which would later help with atomic power and the 'Manhattan Project'.

Rutherford Diagram

1911

Rutherford created an atom diagram which is very well as it has become the symbol for all sciences. He hypothesized that an atom is made up of empty space mostly with electrons orbiting in a set, predictable paths around fixed, positively charged nucleus.

Niels Bohr

1913

Bohr discovered electrons and radioactivity in the atom which would change the model of the atom. His theory explained why atoms emit light in fixed wavelengths.

De Brogile

1924

Brogile hypothesized that not only electrons traveled in waves and that matter have wave properties. Which he then used to help develop the theory for quantum mechanics.

Werner Heisenberg

1925

Heisenberg helped further modify the atomic theory by formulating quantum mechanics and also discovering the uncertainty principle (neither the position or momentum of a particle can be found at an exact point).

Wolfgang Pauli

1925

Pauli created a principle that states that no two electrons in an atom could have identical sets of quantum numbers.

Erwin Schrodinger

1926

Schrodinger is responsible for creating the "Electron Cloud model" a dense nucleus with a cloud multiple orbitals of electrons surrounding the nucleus.

James Chadwick

1932

James Chadwick had a major contribution to the atomic theory by discovering another particle in an atom we know as neutrons. Located with protons in the center of the nucleus with electrons orbiting around it.

Gerhard Herzberg

1937

Herzberg mainly worked on atomic and molecular spectroscopy. He is well known for determining the structure of diatomic and polyatomic molecules.

William Giauque

1949

Giauque contributed most of his life work to establishing the third law of thermodynamics and invented the adiabatic demagnetization cool- ing technique.

Dorothy Hodgkin

1964

Hodgkin was able to determine the molecular structure of penicillin, insulin, and vitamin B12. She used x-rays to find out the structure of these biochemical substances.