Have you ever tried to observe or study something that you could not see? Scientists are faced with this problem each and every day. Geologists must attempt to describe things such as the interior of the Earth or the way in which mountains and deserts came to be. Astronomers attempt to map the outer reaches of the universe. Chemists and physicists across the centuries have been concerned with the smallest particles that make up each and every object in our natural world. Of course, that is the atom. How do scientists study things they can’t see? They make models. A scientific model is a tool constructed by the scientist based on all the known experimental evidence about a particular thing such as an atom. The picture above is an artistic look at one model of the atom, showing the electrons in orbit around the central nucleus. As time goes by and more experiments are performed, models evolve and change to account for new understanding. In this chapter, you will begin to learn about how the model of the atom was initially developed and how it has changed over time into what we now have come to accept as the modern model of the atom.
Opening image copyright Jezper, 2012. www.shutterstock.com. Used under license from Shutterstock.com.