The appearances of the members of the nitrogen group are not similar. Nitrogen being a gas, is colorless and odorless. Phosphorus is found in natural form in white, red and black solid structure. Arsenic exists as a solid with yellow and gray color. The natural state of existence of antimony is metallic or amorphous gray colored substance. Bismuth exists as a white crystalline solid in nature and is a brittle metal. These characteristics are seen as the group members change from non-metals to metals, nitrogen to bismuth.
The physical properties of the group also vary from member to member. Nitrogen is a gas at room temperature and all other members of the group are solids with increasing metallic characteristics. The elements arsenic, antimony and bismuth show characteristics of metals, such as brittleness. Nitrogen liquefies at 77 degrees Kelvin into a colorless and odorless liquid. Phosphorus has two allotropic forms as white and red phosphorus. Arsenic is the only member of the group that can make compounds by sharing three or five of its electrons with other elements.
Nitrogen is inert in nature and does not react easily with other elements and compounds. Nitrogen forms five oxides of with oxygen, with oxidation number of nitrogen ranging from one to five. Important acid of nitrogen are nitric acid and nitrous acid. Phosphorus reacts more than nitrogen with other elements to form phosphides with metals, sulphide with sulfur and halide with halogens. Sulfur catches fire to form sulfur oxide and reacts with alkali metals and acids. An important acid of phosphorus is phosphoric acid used in the production of fertilizers.
Nitrogen, among all the members of the group, finds the most number of uses. It is used in production of fertilizers and explosives. Because of its inert nature, it is also used to create an inert atmosphere free from oxygen. This inert atmosphere can prevent oxidation or combustion of the substance preserved in it. Liquid nitrogen finds use as a refrigerant for rapid freezing of organic substances like food, tissue cultures and sperm cells. Phosphorus finds use in the manufacturing of chemicals like phosphoric acid, fertilizers and detergents. Alloys are made by using arsenic and antimony. These alloys are used to make batteries and special types of solder. Bismuth also finds application in alloy production.