Introduction: Atoms are the fundamental particles of everything around us - from televisions to computers to food. Our understanding of the atom has evolved significantly over time, and it has been applied to a variety of applications in technology and the real world. Oxygen atoms make up what we breathe as part of our atmosphere. Helium atoms exist in a tank of gas, when we inflate balloons. Atoms of oxygen and hydrogen exist in water molecules that comprise what we drink and survive on as human beings.

Atomic theory explains the structure of atoms that makes different elements different from one another. One of the more primitive theories, Dalton's Atomic Theory, formed the crux of discussions about atoms - the fundamental particles of matter. What followed was a consideration of electrons in Bohr's theory of the atom, which included negatively-charged particles called electrons. Next, Rutherford's model of the atom consisted of empty space that surrounded a dense, positively-charged nucleus. After Rutherford's model, the Bohr model of the atom was formulated, consisting of fixed, circular pathways known as orbits. Finally, the wave-mechanical model formed much of today's understanding about electrons, in that they exist in regions of space known as orbitals around the nucleus.

Directions for This Lesson: In this lesson, you will learn about the history of the atom. First, try the practice questions to determine what you already know about the history of the atom. Then, watch the video lesson to learn more about the history of the atom.