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5 BCE
Greek
The Greeks believed that everything is made up of tiny, indivisible particles. The idea originated from the Greek Philosopher, Leucippus and his student, Democritus. Atom comes from the Greek word, Atomos, which means "indivisible" -
Christiaan Huygens
He proved the law of conservation of momentum, which is showing how in a collision the total momentum of both objects is the same before and after the collision. -
Isaac Newton
Isaac Newton is best known for discovering the laws of gravity, but he also made some contributions to the atomic model. He thought that all small solid masses were moving. He understood that atoms weren't stationary but instead, they moved. -
John Dalton
John Dalton was the first person to have a complete attempt at describing matter. He based his theory on the law of conservation of matter, which states that all matter is not created nor can it be destroyed. -
Gustav Kirchhoff
He and Robert Bunsen discovered two alkali metals, cesium and rubidium. The tool they used to find the two metals was called a spectroscope, which they invented a year before. Their discoveries created a new era for new elements to be found. -
James Maxwell
He introduced the concept of the electromagnetic field theory. He made the connection between waves in light and electromagnets. -
Heinrich Hertz
Hertz took the theory Maxwell created and proved it to be true. He proved the existence of electromagnetic waves. He showed that light and heat are electromagnetic radiation. -
Joseph John Thomson
J.J. Thomson found the electron. At the time he was studying cathode rays. Cathode rays are glowing beams of light that follow an electrical discharge. After many experiments he finally concluded that all matter is made up of tiny particles smaller than atoms. At the time he called them 'corpuscles' but we now call them electrons. -
Max Planck
He wanted to find out why radiation going through a human body changes from red, to orange, to blue when the temperature rises. He conducted an experiment and found that at certain temperatures, energy from a human body will occupy different parts of the colour spectrum. -
Plum Pudding Model
J.J. Thomson also came up with the Plum Pudding Model which just shows that electrons are floating around the nucleus. -
Albert Einstein
Albert Einstein saw what Max Planck did and added onto it by saying light can be absorbed or emitted in packets called quanta. Quanta was the opposite of the wave theory of light. -
Ernest Rutherford
Ernest Rutherford conducted the Gold Foil experiment. Rutherford looked at the Plum Pudding model, and from this he knew that the atom had neutrons and electrons, so he conducted an experiment to see if he could add more to the structure of an atom. The Gold Foil Experiment showed him that there was a nucleus in the centre of an atom. -
Niels Bohr
Niels Bohr was the first person to discover that electrons travel in separate orbits around the nucleus. He also discovered that the outer shell determines the properties of an element. After finding out this information he came up with the Bohr Model, which just shows the different orbits of electrons.
