500 bc The first proponents of an atomic theory were the Greek philosophers Leucippus and Democritus who proposed the following model in the fifth century B.C. … Matter is composed of atoms separated by empty space through which the atoms move. 2. Atoms are solid, homogeneous, indivisible, and unchangeable.

alchemy

1700 ce Historically, mass conservation was demonstrated in chemical reactions independently by Mikhail Lomonosov and later rediscovered by Antoine Lavoisier in the late 18th century. The formulation of this law was of crucial importance in the progress from alchemy to the modern natural science of chemistry.

1743 - 1794 Antoine Lavoisier, father of modern chemistry, discovered oxygen, hydrogen, combustion. is credited with law of conservation of mass, though multiple earlier chemists had described the same. executed by guillotine.

1766 - 1844 John Dalton, England, atomic theory The main points of Dalton's atomic theory, as it eventually developed, are:

Elements are made of extremely small particles called atoms. Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties. Atoms cannot be subdivided, created or destroyed. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated or rearranged.

Cathode ray tube experiments to measure weights of gases.

Discovery of electrons as the cathode ray beam.

plum pudding model Rutherford gold foil experiments. Discovery of nucleus

Niels Bohr. the planetary model of the atom.

Rutherford, Bohr, Max plank, and Einstein were contemporaries.

Heisenberg also.

the cloud model 1925 in a breakthrough paper. In the subsequent series of papers with Max Born and Pascual Jordan, during the same year, this matrix formulation of quantum mechanics was substantially elaborated. 1927 He is known for the Heisenberg uncertainty principle, which he published in 1927. 1932 Heisenberg was awarded the 1932 Nobel Prize in Physics “for the creation of quantum mechanics”.[ 1939-1945 Heisenberg worked trying to build nuclear weapons for the Nazis.