The Atom

The atom is the fundamental building block of all stuff, or what scientists like to call "matter". An individual atom is very small. In fact, the smallest type of atom, hydrogen, has a diameter of 10^-8 cm. This means that if the hydrogen atom was the size of a soccer ball, then a soccer ball would be 6450 kilometers (4008 miles) high. Every single object is composed of atoms. Your body is made up of many, many individual atoms. There are also many different types of atoms. In fact, there are over a 100. These different types are called elements. Examples of some elements are hydrogen, oxygen, iron, copper, and helium. Under normal conditions many atoms can stick together to form larger, different stuff. Scientists call material that results from the joining of different types of atoms "compounds". An example of a compound is water, which is a group of two hydrogen atoms and one oxygen atom. Notice that we said that these types of compounds can only form under what we called "normal conditions". In the type of environment in which nuclear fusion occurs, the joining of atoms, also known as bonding, can't happen. We will explain why later.