Lord Rutherford (1911)

Sir James Chadwick (1932)

1932 BCE

1-bombarded beryllium atoms with alpha particles.
2-Chadwick interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton.
3- he discovered the Neutron in atoms. Neutrons are located in the center of an atom, in the nucleus along with the protons. They have neither a positive or negative charge, but contribute the the atomic weight with the same effect as a proton.
4-beryllium atoms with alpha particles.

Niels Bohr

1913 BCE

1-Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities.
2-Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted.
3-Bohr's theory could explain why atoms emitted light in fixed wavelengths.
4-atom based on quantum theory

Lord Rutherford

1911 BCE

1-Physicist Ernest Rutherford established the nuclear theory of the atom with his gold-foil experiment. When he shot a beam of alpha particles at a sheet of gold foil, a few of the particles were deflected. He concluded that a tiny, dense nucleus was causing the deflections.
2-The nucleus was postulated as small and dense to account for the scattering of alpha particles from thin gold foil
3-if you shot a a beam of alpha particles at a sheet of gold sheet
4- the atom has a tiny and heavy nucleus

Sir J.J. Thomson

1897 BCE

1-J.J. Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas
2-in 1897 designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by many scientists at the time
3-he used mathematical formalism to derive inferences from observations.
4- electron by experimenting with a Crookes

Democritus

400 BCE

1-"Atoms" in Greek means "indivisible." Democritus called his discovery this because he believed that the atom was unbreakable into smaller parts.
2-Democritus atomic theory stated that “The universe is composed of two elements
3-if you cut it down constantly it would come to a stop because you can not cut it anymore
4 - The atomic theory or model that was produced.
The atomic theory stated that “The universe is composed of two elements: the atoms and the void in which they exist and move

Timeline of Scientists

Period: 400 BCE to 1932

John Dolton

1808

1-The experiment that they carried out to explore the atomic structure-Experiments with gases
2- The observations that they found
developing the ancient concept of atoms into a scientific theory
3- The inference (explanation of observations) that they made based on their observations-
4-The atomic theory or model that was produced.
Dalton's atomic theory proposed that all matter was composed of atoms