In the early 1800’s, there was a scientist named John Dalton. He wanted to know just how small you could cut a piece of matter until you couldn't cut it anymore. Dalton called this smallest, indivisible piece of matter an atom. He proposed that the atom was an indivisible solid sphere. Over the years scientists gathered evidence to change and refine Dalton’s model of the atom.
Almost 100 years later Dalton’s model of the atom was disproved when a British scientist named, J.J. Thomson discovered that atoms contain negatively charged particles called electrons, proving that atoms were more than a solid, indivisible sphere. Thomas suggested that the atom was made of a thick jelly that was positively charged with negatively charged electrons suspended throughout it. Imagine a ball of chocolate chip cookie dough--where the dough is the positive, jelly-like fluid and the chocolate chips are the electrons.
Six years later, Rutherford decided to test out the Thomson model of the atom by shooting α-particles (which are very small positively charged particles) at a very thin piece of gold foil and observing the alpha particle paths based on where they hit a detector screen.
Let’s recreate the Rutherford experiment and see what happens. Rutherford couldn’t see the atom, but based on the paths of the α-particles, he was able to infer its structure. Can you use inductive reasoning to build a model of the atom?
Use the evidence from Rutherford’s experiment and what you know about how objects travel through empty space and how charges interact to help you build the model.
