- Phosphorus (P) is a multivalent nonmetal with atomic number 15, positioned in Group 15 of the periodic table.
- It has five valence electrons in its outermost shell, giving it the ability to form compounds in oxidation states ranging from –3 to +5. Its atomic structure consists of fifteen protons, typically sixteen neutrons, and fifteen electrons arranged in three shells (two in the first shell, eight in the second, and five in the third).
- Phosphorus has one stable isotope, phosphorus-31 (³¹P), which makes up 100% of natural phosphorus.
- Elemental phosphorus exists in several allotropic forms, the most common being white phosphorus (P₄), red phosphorus, and black phosphorus, each with distinct physical properties and reactivity.
- Phosphorus is the eleventh most abundant element in Earth’s crust and is widely distributed in minerals such as apatite [Ca₅(PO₄)₃(F,Cl,OH)]. It is never found in nature in its elemental form due to its high reactivity but occurs in phosphate minerals and in living organisms as phosphate ions (PO₄³⁻). Industrially, phosphorus is obtained by heating phosphate rock with coke and silica in an electric furnace, producing elemental phosphorus vapor, which is condensed and collected.
- The element was first discovered in 1669 by German alchemist Hennig Brand, who isolated it by distilling residues from boiled urine in search of the “philosopher’s stone.” He named it “phosphorus,” meaning “light-bearer” in Greek, due to its property of glowing in the dark (chemiluminescence) when exposed to oxygen.
- Phosphorus is essential for all known life forms. In biology, it plays a central role in energy transfer through adenosine triphosphate (ATP), is a structural component of nucleic acids (DNA and RNA), and is a key constituent of phospholipids in cell membranes. Phosphate ions also contribute to bone and teeth strength in vertebrates through hydroxyapatite crystals.
- Industrially, phosphorus and its compounds have diverse applications. White phosphorus is used in military smoke munitions and incendiary devices, though its use is restricted due to toxicity. Red phosphorus is safer and is used in safety match strikers, fireworks, and certain flame retardants. Phosphoric acid (H₃PO₄) is a major industrial chemical used in fertilizers, food additives, and rust removal. Phosphates are also key in detergents, though environmental concerns about eutrophication have led to their reduced use in household cleaning products.
- Chemically, phosphorus readily forms covalent bonds with oxygen, hydrogen, halogens, and metals, producing oxides, acids, and phosphides. White phosphorus is highly reactive, igniting spontaneously in air, while red and black phosphorus are more stable. The element’s rich chemistry allows it to participate in a wide range of organic and inorganic reactions, making it critical in both biochemistry and industrial chemistry.
- While phosphorus is vital for life, excessive environmental phosphorus—often from agricultural runoff—can lead to algal blooms and oxygen depletion in water bodies, severely impacting aquatic ecosystems. White phosphorus is highly toxic, causing severe burns on contact and damaging the liver, heart, and kidneys if ingested.
