Lesson 1: Elements and Atoms

Did you know that Earth's crust is composed mainly of oxygen?
The oxygen in Earth's crust is not in gaseous form as it is in the atmosphere. Instead, oxygen is a component of solid compounds, such as rocks and minerals. Elements can exist in various forms. How does the structure of atoms differ when atoms of the same element have different forms?  
In this section, you will review models of the atom, and investigate how these models are used to explain various forms of matter. 

The organization of data into patterns or common characteristics helps scientists understand the material they are studying. In dealing with the matter, elements are classified according to their atomic numbers. The atomic number indicates the number of protons found within the atom. Along with the atomic number, the elements are also categorized according to how they react. The result of this classification is the Periodic Table of the Elements.  Make sure to try the following activity.