Theorized that matter is homogeneous, consisting of small indivisible particles, called atoms which are constantly in motion, and form compounds via collisions. This could be considered the first atomic theory.
Democritus developed Leucippus's atomic theory. He theorized that atoms had space in between each other, were indivisible, and could not be destroyed.
Disagreeing with Democritus, Aristotle believed that the world was made of 4 elements: air, water, fire, and earth. This was perhaps the first theory that elements existed.
Proposed a mechanical universe where small solid masses were in motion.
Proposed matter had positive and negative charges after his famous kite flight is 1752
Stated the first law of conservation of mass in 1789.
Discovered the atom in 1803
Discovered method of splitting molecules using electricity in 1832, later making laws of electrolysis
In 1859, built first functioning cathode ray, which was later used to theorize that atomic particles each contained certain charges.
Discovered that x-rays could pass through solid objects in 1895.
Discovered some chemicals spontaneously decompose and give off penetrating waves.
Found electrons and isotopes, in 1906 was awarded nobel peace prize for discovery of the atom.
Discovered radioactivity in 1898
Discovered the charge and mass of an electron in 1909
His Rutherford model in 1911 theorized that atoms were mostly empty, known as "the father of nuclear physics".
First to show a way to prove the existence of atoms.
Created the Bohr model in 1913, with electrons orbiting around a central nucleus.
Proposed electrons behaved in the matter of an electron cloud.
Discovered neutron in 1932, and theorized the neutron exists to stabilize the atom.
Dicovered that electrons behaved like waves under certain conditions.
Created the Uncertainty Principle, stating that the exact location and energy of an electron cannot be determined simultaneously.
Theorized the Higgs Boson Particle A.K.A. the god particle, in 1964.