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A look back through history UGGH…GA UGGH! (translation: I am the first chemist ever…I have made fire and will be featured in chemistry textbooks for years to come…uggh!) Prior to 8000 BC a period of time known as the Stone Age, humans only had the knowledge to use stone tools. Upon the discovery of fire, fire was used to cook food, fire-harden mud bricks and to make tougher tools. Early chemists were mostly concerned with materials that had high value to humans. This included metals such as gold and copper. Further investigation lead to the discovery of the different properties of copper when heated. Copper was no longer brittle (easily broken), but was soft and malleable. Around 4500 BC, the discovery of combining metals such as copper and tin produced a strong and hard material called bronze. Around 1200 BC a group of people known as the Hittites discovered how to extract iron from rocks and turn it into a useful material. This began the Iron Age. The extension of this was the creation of steel which was produced when carbon was added to iron. Discoveries were often as a result of trying to produce better and stronger weaponry. Democritus – 460 – 360 BCE Around 500 BC there were two versions of the composition of matter. The most believed was the view of Aristotle that everything was made of earth, air, fire, and water. A more accurate view, but less popular was the view of Democritus that everything was made up of different types of atomos. Atomos was the smallest a particle could be broken down into. Until the 1500s individuals known as alchemists continued to conduct experiments, although not to further the understanding of matter, but rather in a search for ways to make gold from other metals. Although not successful, these alchemists developed many chemistry tools and inadvertently made many practical discoveries. Not until the late 1500’s did we begin to see people engaged in activities more like the scientists of today. In the 1660’s Robert Boyle, an Irish scientist experimented on gases under pressure and believed that Democritus’ theories regarding particles was accurate. He believed there were particles of different shapes and sizes that would group together in a variety of ways to make different substances. In the 1770’s Antoine Laurent Lavoisier, a French scientist, studied chemical interactions. By the 1780’s, he had developed a system for naming chemicals. This system standardized the language used and allowed all scientists communicate their ideas in a way that was more easily understood. In 1808, John Dalton developed his own theory of the composition of matter. He suggested that matter was made up of elements. He was the first to define an element as a pure substance that contained no other substances. Dalton also put forth the first modern theory of atomic structure. He believed that each element was made of particles called atoms and that each element had its own kind of atom. His model is sometimes called the “billiard ball model” because he thought of the tiny atoms as solid spheres. JJ Thomson is credited with being the first person to discover a subatomic particle. He showed that negatively charged particles found in beams of light like the one seen in the picture. The particles were called electrons. In 1897, Thomson described the “Raisin Bun” model of the atom. In this model, the atom is a positively charged sphere with negatively charged electrons contained within it. In 1904, Hantaro Nagaoka, refined the model by suggesting that the negatively charged electrons actually surrounded the atom like a planet orbiting the sun. British scientist Ernest Rutherford conducted research at McGill University which is in Montreal. He discovered that the atom has a nucleus at its core. This was discovered by sending high speed particles at thin gold foil. Most of the particles went straight through, others were deflected, however. Niels Bohr of Denmark, suggested that the electrons orbiting a atom do not do so randomly. Rather, the move in circular orbits he call electron shells. He believed that electrons jump between these shells by gaining or losing energy.