Elements

An element is made of only one type of atom. Elements are pure substances. When they join together, they make up everything on Earth. There are 118 elements that we know about. Only 94 exist naturally on Earth and the other 24 are man made.

Even if you aren't sure what an element is, I bet you have heard of some examples! Oxygen is an element. We need oxygen to breathe. We couldn't survive without it. Gold and silver are also elements and so are iron, aluminum, and copper. The helium that makes your balloon float - that is an element too. Even the potassium and calcium in your daily vitamin and the chlorine in a swimming pool are elements.

Not everything is an element though. Many substances are combinations of elements. For example, water is not an element. Water is made of two different elements - hydrogen and oxygen. When two hydrogen atoms and one oxygen atom bond, or stick together, a water molecule is formed. Water is a compound made of two different elements stuck together.

The 118 known elements are organized in a table called the periodic table. Each element is given a number called an atomic number. This number is the number of protons in each atom of that element. An atom of hydrogen has 1 proton so it has an atomic number of 1. An atom of oxygen has 8 protons so its atomic number is 8. Gold's atomic number is 79 because there are 79 protons in each atom of gold.

Elements are listed in number order in the periodic table. They are also grouped together into families that have similar properties. Some of the families you will find in the periodic table include: noble gases, alkali metals, alkali earth metals, transition metals, and nonmetals. Although elements are made from the same type of atoms they can still come in different forms like solid, liquid, or gas.