Chemistry

The name phosphorous is derived from the Greek word for light bearing, phosphoros, from the Greek words phs (light) and phoros (bearer) (Bentor 2010). Phosphorous was discovered by Hennig Brand, a German physician in 1669. His means of isolation though unorthodox lead to the discovery of this very important element. He used roughly 60 buckets of urine for this isolation, by boiling, filtering and otherwise processing as many as 60 buckets of urine (Jefferson, 2010). In this experiment, Henning managed to isolate white phosphorous, characteristic for its white glow upon its exposure to oxygen.  Nowadays phosphorous is obtained from inorganic phosphate rock, calcium phosphate, (Ca3(PO4)2).

Phosphorous is assigned symbol P and has an atomic number 15 and atomic mass 30.973762 amu. Its melting point, boiling point, and density are 317.30 Kelvin (44.15C or 111.47F), 553.65 Kelvin (280.5C or 536.9F) and 1.82 grams per cubic centimeter respectively (cited in Jefferson Lab 2010). Its is found at period three and group 15 of the periodic table. The group name designated is Pnictogen.

Though phosphorous is a white solid non-metal at room temperature, it is a highly reactive element and therefore does not exist in an unbound state. The atomic structure of phosphorous is as follows 2 electrons on the first energy level 8 on the second energy level and 5 on the third energy level with the following electronic configuration  HYPERLINK httpen.wikipedia.orgwikiNeon o Neon Ne 3s2 3p3. Phosphorous has no isomers, but has 23 isotopes for example P24, P25, P26, P31, P32, P33 etc 22 of which are radioactive and only P31 as stable. Three allotropes of phosphorous are known black, white and red with white being its original form. Both black and red phosphorous are obtained by heating white phosphorous (250C for red) or by exposing it to sunlight, but for the production of black phosphorous mercury catalyst and a seed crystal of black phosphorous are required (cited in Jefferson Lab 2010).

Phosphorous can react with other elements, compounds and acids to form phosphorous compounds. Phosphorous pentoxide also known as tetraphosphorus decaoxide, P4O10, is formed by the reaction of phosphorous and oxygen. P4(s)  5O2(g)  P4O10(s)

It appears as a white crystalline solid and has a melting point(mp), boiling point (bp), and density of 422C 605C and 2300 kg m-3

Phosphorous trioxide also known as tetraphosphorus hexaoxide, P4O6, can also be formed via reaction with oxygen, though the conditions must be controlled.  Under careful control (75 O2, 25 N2, 50C, 90 mm Hg), a mixture is formed, one of the products phosphorus trioxide  (Webelements 2010). P4(s)  3O2(g)  P4O6(s). It appears as a white crystalline solid. Its mp 23.8C, bp 173C and density 2130 kg m-3.

White phosphorus, P4, reacts vigorously with all the halogens at room temperature to form phosphorus trihalides (Webelements, 2010). Examples of halogens include chlorine, bromine iodine and fluorine. Phosphorous(III) fluoride formed through the following reaction,
P4(s)  6F2(g)  4PF3(g)
                                       ..
P
                                           F                   F
                                                   
                                                      F

  Colourless gas with mp of -152C bp -102C and density 3.8 kg m-3 (gas)  (Webelements, 2010).
Diphosphorous tetraflouride can also be formed through the reaction of phosphorous and fluorine. P4(s) F2(g)  P2F4(g) It appears as a colourless gas with a mp of -86.5C.

Phosphorus(III) chloride, formed through the following reaction, P4(s)  6Cl2(g)  4PCl3(l)
                               ..
P
                                           Cl                   Cl
                                                   
                                                      Cl

It appears as a colourless liquid with mp of -112C, bp of 76C and density 1575 kg m-3 (cited in Webelements 2010).
Phosphorus(III) iodide, formed through the following reaction, P4(s)  6I2(g)  4PI3(g)
                              ..
P
                                             I                   I
                                                   
                                                      I

Appears as a white crystalline solid with a bp of 227C, mp 61C and density 4200 kg m-3.
Phosphorous(III) bromide, obtained through, P4(s)  6Br2(g)  4PBr3(l)

                               ..
P
                                           Br                   Br
                                                   
                                                      Br

This appears as a colourless liquid with a mp of -41.5, C bp of 173.2 C and density of 2.852 gcm3, it is very soluble in water.

A different reaction can be seen with bromide. Where phosphorus(V) bromide is formed. 2P5(s)  5Br2(g)  2PBr5(s)

                                                      Br
                                     
P
                                            Br                 Br
                                                 Br        Br


It is seen as an orange crystalline solid with a melting point above 100C and a boiling point of 106C and a density of 3600 kg m-3.

White phosphorous can react with iodine under special conditions to form phosphorus(II) iodide. White phosphorus, P4, reacts with iodine, I2, in carbon disulphide (CS2) to form, P2I4 (Webelements,2010). P4(s)  4I2(g)  2P2I4(g)
  I
 
IP-PI                         This occurs as a red solid with a melting point of 125.5C
       
        I
Diphosphorous tetrahydride, occurs as a result of the reaction of hydrogen and phosphorous. P4(s)  4H2(g)  2P2H4(g)
 H