Pnictogen

Pnictogen is the term for the elements in group 15 of the periodic table. This group includes nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), and moscovium (Mc), a synthetic element with an extremely short half-life.

Common characteristics of the group include the fact that each atom has five electrons in its outermost shell (general configuration s²p³). This allows them to form three covalent bonds or operate at different oxidation states, particularly +3 and +5 for the heavier elements.

Name and origin

The term derives from a Greek root relating to "breathing" or "choking breath," used because nitrogen alone does not support respiration. The term is widely used in scientific chemistry writing, though the alternative name "nitrogen group" is also common.

Change in properties down the group

Nitrogen is a nonmetallic gas; phosphorus is also nonmetallic and exists in various forms (allotropes) such as white phosphorus and black phosphorus. Arsenic and antimony are classified as metalloids—substances intermediate between metals and nonmetals. Bismuth is considered a metal. Accordingly, moving down the group, metallic character increases while electronegativity decreases.

Important compounds

The group forms hydrides such as ammonia (NH₃) and phosphine (PH₃), which differ greatly in their properties. Oxides and acids derived from them—such as nitric acid and phosphoric acid—are fundamental to fertilizer manufacturing and chemical industry. Atmospheric nitrogen and phosphorus in soil are among the most economically important elements.

Role in life and applications

Nitrogen and phosphorus are essential elements for living organisms: nitrogen is present in amino acids and nucleic acids, while phosphorus is part of the backbone of DNA and molecules that transfer energy within cells. Arsenic and antimony are used in electronic devices and metal alloys, though certain arsenic compounds are toxic.