After reading this section you will be able to do the following:

  • Be able to define an element.
  • Be able to recognize and recall some of the basic elements.

Elements Defined

Any material that is composed of only one type of atom is called a chemical element, a basic element, or just an element. Any material that is composed of more than one type of atom is called a compound. Every element has a unique atomic structure. Scientists know of only about 109 basic elements at this time. (This number has a habit of changing.) All matter is composed of combinations of one or more of these elements. Ninety-one of these basic elements occur naturally on or in the Earth. The other elements are man-made. You may recognize the names of some of these basic elements, such as: hydrogen, helium, oxygen, iron, copper, gold, aluminum, uranium. The periodic table of elements (shown below) lists the basic elements and some of their properties.

The periodic table is organized based on the atomic number of each element, which is located in the top left corner of each element box in the table below. The atomic number is the number of protons in the nucleus of an atom of that element. The atomic mass is also listed for each element below under its name. 

The periodic table also tells us about the state of matter each element is in at room temperature. While most elements are solids at room temperture, 11 elements, including Hydrogen, Helium, and Oxygen, are gases at room temperature and 2 are liquids.

Image of the Periodic Table


  1. An element is material composed of only one kind of atom.
  2. A compound is material composed of more than one kind of atom.
  3. The periodic table lists out the known elements and describes some of their properties.