Democritus, a Greek philosopher, noticed that when he split a rock in half, the two halves were the same. He theorized that if he continued splitting the rock pieces in half, he would get smaller and smaller particles of identical composition. The called these small particles “atomos”, Greek meaning “undivided”. At the time, his theory was rejected by his peers and the theory of atoms did not resurface until the 1800s.

In this section, we will look at the structure of matter and how scientific experimentation led to an understanding of the structure of the atom. We will also look at safe laboratory practices, identify historical uses of chemistry, and investigate some chemistry-based careers.

1. learn about WHMIS pictograms and safe practices in the handling of chemicals in the laboratory and at home
   

2. identify the laboratory evidence that scientists such as Dalton, Thomson, Rutherford, and Bohr collected during the development of the atomic model, which consists of protons, neutrons (nucleons) and electrons
   

3. identify historical examples of how humans used chemical substances and identify examples of chemistry-based careers in your community