What is Phosphorus? - Element Uses, Facts & Properties

Instructor: Sarah Pierce

Sarah has a doctorate in chemistry, and 12 years of experience teaching high school chemistry & biology, as well as college level chemistry.

This lesson describes the properties and uses of three different allotropes of the element phosphorus: red, white, and black. Additionally, the biological role of phosphorus is discussed.

Lighting Fires

Imagine that you are camping and need to light a fire to roast marshmallows. You reach for your trusty box of matches and pull one out. You run the match over a panel on the side of the box and it magically lights. Have you ever wondered what the stuff on the panel is? It's phosphorus! Let's find out more about this element that helps light your fire.

Phosphorus is used as an igniter for matches
match

Facts About Phosphorus

Phosphorus is in Period 3 and Group 15 of the periodic table. It has 15 protons, so it has the atomic number 15. This also means it is the 15th element on the periodic table. The chemical symbol for phosphorus is P.

Phosphorus is in Period 3 and Group 15 on the periodic table
periodic

Properties and Uses of Phosphorous

The three main types of elemental phosphorous are red, white, and black. These are allotropes, or different molecular forms. Allotropes have different arrangements of atoms from each other. Each of these phosphorous types have different properties and uses.

Red Phosphorus

Red phosphorus is the most common form of phosphorus. It is amorphous, meaning that the atoms are randomly arranged. Red phosphorus is not toxic and primarily used as an igniter for matches.

Sample of red phosphorus
red

White Phosphorus

White phosphorus is poisonous and can burn you if it touches your skin. It exhibits chemiluminescence, or an emission of greenish light, when it is in the presence of oxygen molecules. White phosphorus is also pyrophoric, meaning that it can ignite spontaneously when it is exposed to air. It is primarily used in bombs for warfare.

A white phosphorus bomb used in the Vietnam War
white

Black Phosphorus

Black phosphorus is very stable and can conduct electricity. However, black phosphorous is very hard to synthesize because it requires very high pressure. While it may be used one day in electronic devices, it is currently not used in any applications.

Biological Importance

Phosphorus is the sixth most abundant element in the body. Your teeth and bones are made of calcium phosphate, which has phosphorus atoms. Phosphorus is part of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). It is also a component of adenosine triphosphate (ATP), the energy transfer molecule in cells. Phosphorous is even found in phospholipids that create the cell membrane.

ATP contains phosphorus atoms
atp

Fertilizer

Phosphorous, as part of the ion phosphate (PO 4 3-), is also important for growing crops. One of the major industrial uses of phosphorous is in the manufacturing of fertilizer. Phosphate ore is used to make the fertilizer ammonium phosphate.

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