Chemistry is a branch of science that has been around for a long time. Chemistry dates back to prehistory. Chemistry has been around so long that scientists have classified it into 4 general chronological categories. These four categories are prehistoric, early Christian era, late 17th century (alchemy), traditional chemistry, and modern chemistry. Some of the very first recorded chemists were men like Democritus and Aristole. These men lived in the BC era and have a lot of influence on how we do modern chemistry today. Starting with Democritus, the man who argued that the atom is the simplest unit of matter. Democritus of ancient Greece posed the question of whether matter could be divided into smaller and smaller pieces forever or was there a limit to the number of times a piece of matter could be divided? Democritus had a theory that it would eventually become too small to cut. This piece would no longer be able to divide. He called this indivisible matter atomos. For Democritus of Greece, atoms were small, hard particles, all made of the same material but of different shapes and sizes. He said they were always on the move and able to come together. Aristotle of ancient Greece added to the theory by declaring the existence of our only four elements: Fire, air, water and earth. All matter is made up of one of these four elements, and matter is made up of these four elements, and matter has four properties: hot, cold, dry, and wet. Aristotle was born in Stagira, northern Greece, the son of Nicomachus, the court physician of the Macedonian royal family. He initially studied medicine, but was later sent to Athens and became a philosopher under a man named Plato. Alchemy is what became the...... middle of paper... each charge had a mass ratio of 1.759E8 coulombs per gram. He concluded that all atoms have this negative charge (through further experiments) and renamed cathode rays electrons. His model of the atom showed a sphere of positively charged material with negative electrons stuck inside it. Thomson received the Nobel Prize in Physics in 1906. James Chadwick discovers the neutron. Enrico Fermi bombards the elements with neutrons and produces elements with the next highest atomic number. Nuclear fission occurred when Fermi bombarded uranium with neutrons. He received the Nobel Prize in Physics in 1938. Albert Einstein was also probably the greatest contributor to chemistry. He was part of a group of scientists who embarked on a mission to create an atomic fission reaction. It was known as the Manhattan Project and created the greatest chemical invention ever: the atomic bomb.