Properties & Uses of Compounds of Group 5 Elements

Instructor: Allyn Torres

Allyn has taught high school chemistry, and has a master's degree in curriculum and instruction.

In this lesson, you will learn about the preparation, properties, and uses of compounds found in group 5 on the periodic table. The compounds include oxides of nitrogen, phosphorus trichloride, phosphorus pentachloride, and oxoacids of phosphorus.

Compounds of Group 5 Elements

The title of this lesson doesn't really do the topic justice. Compounds made from elements in Group 5 of the periodic table can help athletes increase endurance and build muscle. They're involved in making chemical weapons used in war. And, you might even them find in your favorite beverages.

Oxides of Nitrogen

Oxides of nitrogen are compounds made from a combination of nitrogen and oxygen. These compounds are typically in gaseous form. Common oxides of nitrogen are nitric oxide, nitrogen dioxide, nitrous oxide, and nitrogen pentoxide.


Many oxides of nitrogen are prepared through the organic process of nitrogen fixation. There are different ways that nitrogen fixation can occur. Oxides of nitrogen are made when lightning passes through the air. This type of nitrogen fixation causes nitrogen gas in the atmosphere to combine with oxygen gas to form compounds like nitric oxide. These compounds are later carried down into the soil.

A compound that many of us are familiar with is nitrogen dioxide. Nitrogen dioxide is often formed from emissions from motor vehicles. Nitric oxide is in the atmosphere due to the combustion reactions that take place inside the engines of vehicles. When the nitric oxide combines with the oxygen in the air, nitrogen dioxide is formed. Nitrogen dioxide is thought to be a source of air pollution.


Oxides of nitrogen are often in a gaseous state. Their color and odor depend on the particular gas. For example, nitric oxide is a colorless gas with a sweet smelling odor, and nitrogen dioxide is a reddish-brown gas with an irritating odor. Oxides of nitrogen often have low melting and boiling points (below 0 °C). They are often more dense than air, which means air will float on top of oxides of nitrogen.


There are various uses for oxides of nitrogen. Nitric oxide is very useful to the human body. Body builders and athletes have found nitric oxide to be useful in helping them build their endurance and increase muscle mass. Nitric oxide helps break down lactic acid (a fatigue-causing chemical that can build up in muscles during exercise). Increasing nitric oxide levels in the body can also aid in the treatment of erectile dysfunction and heart disease.

Nitrogen dioxide can be used to make explosives. When nitrogen dioxide is dissolved in water, nitric acid molecules are formed. Nitric acid is a key ingredient used to make explosives such as TNT.

Another oxide of nitrogen, nitrous oxide (commonly known as 'laughing gas') is used in many dental procedures. It is used to control pain and as a numbing agent during oral surgery. The nickname 'laughing gas' was given to it due to its ability to make people under the influence of nitrous oxide feel happy. Nitrous oxide is also used in race cars in order to enhance engine performance.

Phosphorus Trichloride

Phosphorus trichloride is a compound made of one phosphorus atom bonded with three chlorine atoms. It is typically in liquid form.


Phosphorus trichloride is formed from the reaction of white phosphorus and chlorine gas. It is often manufactured in chemical plants.


Phosphorus trichloride is a colorless liquid that releases smoke. It has a very strong odor. It has a boiling point of 75 °C and a melting point of -112 °C. It is also not flammable.


Phosphorus trichloride is used as a chemical intermediate in manufacturing other chemicals. A chemical intermediate is a middle step in a chemical reaction. Many chemical reactions do not occur in one simple step but in several steps. A chemical intermediate acts like a 'middle man' between the chemicals that go into a reaction (reactants) and the chemicals that come out of the reaction (products). Phosphorus trichloride goes into the manufacturing of pesticides, flame retardant materials, chemicals used in water treatment, and plastic additives. It is also used to make chemical weapons (such as nerve gas).

Phosphorus Pentachloride

Phosphorus pentachloride is a compound made of one phosphorus atom and five chloride atoms. It is typically a solid.


Phosphorus pentachloride is made in manufacturing plants. It is prepared using a reaction where a mixture of phosphorus trichloride and carbon tetrachloride is put into a container and stirred. Chlorine is then introduced into the mixture and crystals are formed in the liquid. The phosphorus pentachloride crystals are then strained from the liquid.


Phosphorus pentachloride is a greenish-yellow solid that has a crystal structure. It has an irritating smell. It can have a corrosive effect on metal and human body tissues. It will sublimate (go directly from a solid to a gas) at 159 °C. It is more dense than water, which means it will sink in water.

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