Democritus was the first scientist to suggest that all matter was composed of small, indivisible particles and that the properties of matter was determined by the properties of these pieces of matter.
Dalton was the first scientist to theorize that atoms of different elements had different weights and proposed a number of ideas about the atom that remains true today.
Because of his Perforated Cathode Ray experiment, Goldstein concluded that atoms had a positively charged particle, the proton, because they flew through the holes in the negative cathode. He is also credited with the discovery of canal rays.
Thomson discovered the electron through a series of experiments. He concluded that electrons were much smaller than the actual atom and the charge to mass ratio was very large. Thomson also did experiments with cathode rays.
Max Planck was responsible for the discovery of the quantum theory, stating that energy must be released in small quantities rather than in a continuous wave and explained atomic emission spectra through the quantum theory.
Einstein argued that light energy was released in small packets called quanta. He was also the one to discover the quality of mass and energy, e=mc2.
Millikan used his Oil Drop Experiment to prove the charge and mass of an electron. He also concluded that changes in energy occurred in tiny increments, proving the Quantum Theory.
Rutherford theorized that an atom had a very dense, positively charged core, due to particles being deflected by a sheet of gold foil, and that negatively charged electrons orbited the nucleus like planets around the sun.
In contrast to Mendeleev's periodic table, Moseley ordered his table by atomic number and wavelengths of x-ray spectral lines rather than atomic weight.
Bohr applied quantum theory to Rutherford's atomic structure involving orbiting electrons. Bohr concluded that electrons traveled in stationary orbits, but this also led to the discovery of energy levels and that there is a limited number of electron energies allowed.
de Broglie was the scientist to introduce the theory of wave/particle duality, suggesting that particles act like waves and that waves act like particles. This was described by the equation λ=h/p, where λ is wavelength, h is Planck's constant, and p is momentum.
Heisenberg discovered that knowledge of the exact location and momentum of particles at the atomic level wasn't possible. Observation required light, and the energy from the light would alter the position and momentum of whatever was being observed.
Schrodinger, known for his quantum mechanical model, took the theories and ideas of other scientists before him and put them together to come up with his own equation. This equation proved that energy was quantized and that orbitals were essential to electron location. This equation explained chemical properties and reactivity of elements.
In 1932, James Chadwick discovered the neutron, a neutrally charged particle in the nucleus. His discovery ultimately lead to the fission of uranium-235 and the making of the atomic bomb.
Discovered oxygen, carbon monoxide, and nitrogen dioxide
Considered the father of modern chemistry due to his discovery of the law of conservation of matter.
Invented the world's first battery.
Considered one of the saviors of mankind because of the importance of Pasteur's discovery of the pasteurization process.
First to transmit and receive a radio wave.
Discovered radiation of uranium
Much of his will went to establishing the Nobel Prize.
First to isolate insulin
Invented the television
Created the first electric generator
Invented the nuclear chain reaction and the atomic bomb
Discovered the polymerase chain reaction