History of the Atom timeline.

He beilieved that objects, like stone, could be cut up into smaller pieces until there was a piece that was undividable. He called these pieces “atomos” which is the Greek word for undividable. He also believed that there were atoms of different sizes and shapes and could be bound or stuck together during collisions. His theory was rejected by Aristotle and was ignored for almost 2,000 years. Democritus believed that everything in the universe was made out of atoms.

John Dalton came up with the atomic theory. His theory stated that all matter is made of atoms and arr indivisible and indestructible, all atoms of a given element are identical in mass and properties, compounds are formed by a combination of two or more different kinds of atoms and a chemical reaction is a rearrangement of atoms. He created his theory in 1803. He formed this theory by doing experiments on gases.

J. J. Thompson was an English scientist who discovered the electron when he was experimenting with gas discharge tubes in 1897. He discovered a movement that he called cathode rays that moved from the negative end of the tube to the positive end. From observing that movement, he concluded that the rays were made of negatively charged particles, which he called electrons.

Ernest Rutherford, in 1911, discovered that an atom had a small charged nucleus that was surrounded by mostly empty space and that electrons surrounded it. This became know as the Rutherford model, or the planetary model, of the atom. He made this discovery when he conducted an experiment called the gold foil experiment, in which he used a thin sheet of gold foil and shot alpha particles at it. He saw that most particles passed straight through it, but some went straight back or were deflected.

Niels Bohr was a Danish physicist who made a model of the atom in 1913. The model he made was similar to the model of the solar system. It depicted th atom as a small, positively charged nucleus surrounded by negatively charged electrons that traveled in circular orbits. Bohr made it so that each electron energy level was different from the others and could hold different a different amount of electrons. The energy of each electron increased from level 1 to other levels.