History of Atoms timeline.

Democrtus expanded the atomic theory of Leucippus. He discovered that all matter is made up of invisible particles called atoms. He hypothesized that atoms cannot be destroyed, are always moving, differ in size, and are invisible. He was born in Abdera, but traveled a lot, like Eygpt, India, Babylon, and Persia. He was the first scientist to create a model of the atom. The model a round solid ball, but it helped give people a better understanding of the idea of an atom.

The "father of modern chemistry". He stated the first version of the law of conversation of mass. Lavoisier believed that matter was neither created or destroyed in chemical reactions. He was intent on collecting and weighing all the substances involved in the reactions he studied. Antoine showed that the mass of a products in a reaction are equal to the mass of the reactants. He was the first to prove that matters shape may change, but it's mass will stay the same.

Dalton created the atomic theory of matter, he included in his theory that atoms cannot be created or destroyed, all matter is made up of atoms. He also found that different atoms from other elements combine in whole ratios to form chemical compounds. While he was researching gases he discovered that certain gases could only be combined in certain proportions, even if the different compounds shared the same common element or elements. The experiments built upon the theory.

Thomson discovered the electron. He discovered that cathode rays were negatively charged & studied positively charged particles in neon gas. He found this by creating the "plum pudding" atomic model.Thompson had discovered that atoms are composite objects, made of pieces with positive and negative charge and that the negatively charged electrons within the atom are very small compared to the entire atom.

She wanted to see if there was any other elements that radiation. She soon discovered that thorium also emitted radiation and that the amount of radiation depended on the amount of element present in the compound.She found that the intensity of radiation is proportional to the amount of uranium or thoriurm in the compound, no matter what the compound is. Curie found this with her husband, Pierre Curie.

Planck is best known as the originator of the quantum theory of energy. Planck realized that light and other electromagnetic waves were emitted in discrete packets of energy that he called "quanta".Planck noted that the energy of photons could only take on certain discrete values which were always a full integer multiple of a certain constant. Therefore light and other waves were emitted in discrete packets of energy know as "quanta".

Albert was one of the greatest scientists of all time. He came up with the theory of relatively, the idea that only relative motion can be measured. Einstein's theory is embodied in his famous equation E=mc2. Although light photons don't have mass, they have energy, and Einstein's theory says that even pure energy has to behave in some ways like mass.

Millikan was interested in J.J Thomson's finding of the electron. He wanted to prove that the electron was 1000 times smaller than the atom. To prove this Millikan did the "oil drop" experiment.Then x-rays were used to ionize the air, by removing electrons from the electrons droplets that captured one or more electrons were attracted to the positive plate by carefully studding these droplets Millikan was able to show that the charge of a drop was an integral multiple of a small value.

Bohr's greatest contribution was the atomic model. The atomic model shows the atom as a small, positively charged nucleus surrounding by orbiting electrons. He was the first to discover that electrons travel in separate orbits around the nucleus and that the number of of electrons in the outer orbit determines the properties of an element. He used Planck's theory to help him figure out the atomic model.

Louis believed that electrons can act like both particles and waves, just like light. He also said that waves produced by electrons contained in the orbit around the nucleus, set up a standing wave of energy, frequency, and wavelength.By rearranging an equation he derived a relationship between one of the wave-like properties of matter and one of its properties as a particle.

Ernest felt like J.J Thomson's model was incorrect so he created a new one. He was the first to discover that atoms have a small charged nucleus surrounded by mostly empty space and are circled by tiny electrons.The Rutherford Gold Foil experiment shot tiny particles at a thin sheet of gold. A small percentage of the particles were deflected, while a majority passed through the sheet.This then caused Rutherford to conclude that the mass of an atom was concentrated at the center.

Erwin, an austrlan physicist, took the Bohr atom model one step further. This atomic model is known as the quantum mechanical model of the atom. Unlike Bohr's model, this model doesn't define the exact path of an electron, but predicts the odds of the location of the electron. He used mathematical equations to describe the likelihood of finding an electron in a certain position. His model can be portrayed as a nucleus surrounded by an electron cloud.

Werner calculated the behavior of electrons, and subatomic particles that also make up an atom. His discovery helped clarify the modern view of the atom because scientist can compare the few numbers of atoms that there are by their movements of electrons, and how many electrons an atom contains. Werner included quantum mechanics, the branch of mechanics, based on quantum theory, used for interpratating the behavior of elementary particles and atoms

Chadwick was an English scientist that discovered the neutron. He started to question why there was a difference between the atomic mass and the number of protons. Chadwick later found that the missing item was a neutral part, the neutron.The gamma ray source had been the radioactive element polonium. Chadwick drew the conclusion that the protons had actually been hit by the particle he was looking for, the neutron. He then did his own experiment of this and discovered the neutron.