Essay On Atomic Theory

An atom is a basic unit of an element. For thousands of years, people have been questioning about these tiny particles and have came up with many theories based around it. Though many people believe atomic theories started with John Dalton around the late 1700s or early 1800s. This is not true as the atomic theories started sometime during 300 or 400 B.C. with the philosopher, Democritus, being one of the first to come up with a theory about atoms. Democritus’ theory gave the basics of an atom; but his theory was rejected by many during his time as fellow philosophers, Aristotle and Plato, rejected his theory ("The History of the Atom"). After hundreds of years, the theory came back and was formed into what we now know as the modern atomic …show more content…
Dalton was the first to describe all matter in terms of atoms and their properties. Dalton based his theory on the law of constant composition and the law of conservation of mass. The law of conservation of mass states that matter cannot be created or destroyed. The law of constant composition states that a pure compound will have the same proportions as the elements used to make it. His theory states that all matter are made of atoms and that these atoms are indivisible, meaning that the atoms cannot be divided. Thus, this explains why matter does not change and why the proportions of an atom does not change. The theory goes on to state that all atoms of an element have identical mass and properties to the element that the atom is in. The theory also that compounds are created by combining two or more types of atoms. Lastly, Dalton says that chemical reactions are just the rearrangement of theories ("Dalton 's Atomic Theory"). Dalton also had a atomic model to go with his theory. Dalton’s model is called the Billiard Ball Model. The model is just a circle with nothing inside it, much like Democritus’ model ("Dalton 's Billiard Ball …show more content…
Rutherford did an experiment where he hit a thin piece of gold foil with alpha particles and was able to see the alpha particles pass through the gold foil. Alpha particles are positively charged due to the losing their electrons. This made Rutherford realized two things. He realized that atoms are made mostly made of empty space and that the positively charged particles, called a proton, were all packed together in a place called the nucleus. Rutherford made a model that fits his new atomic theory. The Rutherford model is a circle with a few smaller circles within it, one small circle in the middle to represent the proton and the other small circles represent electrons ("Atomic