As an element, phosphorus exists in two major forms—white phosphorus and red phosphorus—but because it is highly reactive, phosphorus is never found as a free element on Earth.
The vast majority of phosphorus compounds mined are consumed as fertilisers. Phosphate is needed to replace the phosphorus that plants remove from the soil, and its annual demand is rising nearly twice as fast as the growth of the human population.
The predominant source of phosphorus in modern times is phosphate rock (as opposed to the guano that preceded it).
Protons and Neutrons in Phosphorus
Phosphorus is a chemical element with atomic number 15 which means there are 15 protons in its nucleus. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10-19 coulombs.
The total number of neutrons in the nucleus of an atom is called the neutron number of the atom and is given the symbol N. Neutron number plus atomic number equals atomic mass number: N+Z=A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N – Z = A – 2Z.
For stable elements, there is usually a variety of stable isotopes. Isotopes are nuclides that have the same atomic number and are therefore the same element, but differ in the number of neutrons. Mass numbers of typical isotopes of Phosphorus are 31.
Main Isotopes of Phosphorus
23 isotopes of phosphorus are known, ranging from 25P to 47P. Only 31P is stable and is therefore present at 100% abundance.
Phosphorus-31 is composed of 15 protons, 16 neutrons, and 15 electrons. The half-integer nuclear spin and high abundance of 31P make phosphorus-31 NMR spectroscopy a very useful analytical tool in studies of phosphorus-containing samples.
Phosphorus-32 is composed of 15 protons, 17 neutrons, and 15 electrons. 32P, a beta-emitter (1.71 MeV) with a half-life of 14.3 days, which is used routinely in life-science laboratories, primarily to produce radiolabeled DNA and RNA probes.
Phosphorus-33 is composed of 15 protons, 18 neutrons, and 15 electrons. 33P, a beta-emitter (0.25 MeV) with a half-life of 25.4 days. It is used in life-science laboratories in applications in which lower energy beta emissions are advantageous such as DNA sequencing.
Electrons and Electron Configuration
The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. Therefore, the number of electrons in neutral atom of Phosphorus is 15. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z – 1) negative electrons in the atom.
Since the number of electrons and their arrangement are responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.
Electron configuration of Phosphorus is [Ne] 3s2 3p3.
Possible oxidation states are +3,5/-3.
As an element, phosphorus exists in two major forms—white phosphorus and red phosphorus—but because it is highly reactive, phosphorus is never found as a free element on Earth. The most prevalent compounds of phosphorus are derivatives of phosphate, a tetrahedral anion. Phosphate is the conjugate base of phosphoric acid, which is produced on a massive scale for use in fertilisers.
Most Common Compound of Phosphorus
Phosphoric acid is a weak acid with the chemical formula H3PO4. Food-grade phosphoric acid is used to acidify foods and beverages such as various colas and jams, providing a tangy or sour taste. Soft drinks containing phosphoric acid, which would include Coca-Cola, are sometimes called phosphate sodas or phosphates.
|Number of protons||15|
|Number of neutrons (typical isotopes)||31|
|Number of electrons||15|
|Electron configuration||[Ne] 3s2 3p3|
Properties of other elements