Periodic Table


Atomic number: 15
Atomic weight: 30.973761
Symbol: P
Group number: 15
Electronic configuration: [Ne].3s2.3p3


It is an essential component of living systems and is found in nervous tissue, bones and cell protoplasm. Phosphorus exists in several allotropic forms including white (or yellow), red, and black (or violet). White phosphorus has two modifications. Ordinary phosphorus is a waxy white solid. When pure, it is colourless and transparent. It is insoluble in water, but soluble in carbon disulphide. It catches fire spontaneously in air, burning to P4O10, often misnamed as phosphorus pentoxide. When exposed to sunlight, or when heated in its own vapour to 250°C, it is converted to the red variety. This form does not ignite spontaneously and it is a little less dangerous than white phosphorus. The red modification is fairly stable and sublimes with a vapour pressure of 1 atmosphere at 417°C.

General information

Discoveror: Hennig Brand
Date discovered: 1669
Discovered at: Germany
Meaning of name: From the Greek word "phosphoros" meaning "bringer of light" (an ancient name for the planet Venus?)

Physical data

Standard state: solid at 298 K
Colour: colourless/red/silvery white
Density of solid at ambient temperature/kg m-3: 1823
Molar volume/cm3: 17.02

Radii /pm

Atomic: 98
Covalent (single bond):
Pauling radius for the ion [P]-: 279

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius83.797.8no datano data


Both values are quoted on the Pauling scale.

Pauling: 2.19
Allred Rochow: 2.06

Crystal Structure

structure: triclinic

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 317.3
boiling point: 550

Enthalpies /kJ mol-1

fusion: 0.66
vaporization: 12.4

single bond enthalpies:
P-F P-Cl P-Br P-I P-P
490 326 264 184 489.5

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
31P30.9737620 (6)100

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/P.html