Phosphorus (P)
Phosphorus is the 15th element, a reactive nonmetal in the p-block. Its standard atomic weight is 30.974.
Phosphorus
30.974
What the table records
- Atomic number
- 15
- Standard atomic weight
- 30.974
- Group
- 15
- Period
- 3
- Block
- p-block
- Category
- Reactive nonmetal
- [Ne] 3s2 3p3
- Valence electrons
- 5
- Typical valence
- 3
- Van der Waals radius
- 1.95 Å
- Covalent radius
- 1.07 Å
Molecules containing phosphorus
The lightest named structures in this library that contain P.
Phosphorus
P · 30.97 g/mol
Phosphine
H₃P · 34 g/mol
Phosphonium
H₄P+ · 35.01 g/mol
Oxidophosphanium
H₃OP · 50 g/mol
Dioxidophosphane
HO₂P-2 · 63.98 g/mol
Phosphinic Acid
H₃O₂P · 66 g/mol
PMe3
C₃H₉P · 76.08 g/mol
Trimethylphosphanium
C₃H₁₀P+ · 77.09 g/mol
Fluorophosphite
FO₂P-2 · 81.97 g/mol
Phosphonic acid
H₃O₃P · 82 g/mol
Phosphorous acid
H₃O₃P · 82 g/mol
Phosphonium, tetramethyl-
C₄H₁₂P+ · 91.11 g/mol
How to read these numbers
The standard atomic weight is an average over the isotopes as they occur naturally, which is why it is rarely a whole number. It is the figure a molar mass calculation uses. Work in mass spectrometry wants the monoisotopic mass of a single isotope instead, which is a different number.
The two radii are not the same measurement. The covalent radius is half the distance between two bonded atoms of the element; the van der Waals radius is how close a non-bonded atom gets before repulsion takes over, and is always the larger. Space-filling models are drawn with the second, ball-and-stick models with the first — which is why the same molecule looks so different in the two.