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Phosphorus Discovery

Phosphorus is a very essential element. Apart from its role in the sustenance of life, it also has many monetary benefits. The element was observed by a German pharmacist and alchemist Henning Brand in 1669. He discovered it as he used to be searching for the mythical valuable stone by concentrating urine through evaporation. The title phosphorus is derived from Greek ‘phosphorous’ which means bringer of light. Moments after heating white phosphorus which deposited at the bottom of the flask when the air used to be excluded. Phosphorus is represented by the symbol P in chemical representation. Phosphorus is in length 3 and group 5 of the periodic table. The aspect has atomic number 15 and an electronic configuration of [Ne]3S23P3. The density of phosphorus is 1.823gm3, and it is a solid at room temperature. It has a yellow appearance. Some phosphorus has a variety of color ranging from scarlet, red to black.

Isotopes

There are twenty three known isotopes of phosphorus. Amongst all the isotopes, it is the only 31P that is stable and therefore represents 100% of phosphorus abundance on the earth surface. The element (31P) has a half spin in the Nuclear Magnetic Resonance (NMR) which makes it very useful in analytical studies. All other isotopes of phosphorus are radioactive and disintegrate into other elements with time.

Allotropes of Phosphorus

There are three types of phosphorus; black phosphorus, white phosphorus and red phosphorus. The black phosphorus has three crystalline and one amorphous modification with a density of 2.689g/cm3. Black phosphorus is formed when white phosphorus are subjected to high pressure. It is grey-black and has a structure that closely resembles that of graphite. Black phosphorus also has the semi-conducting properties seen in graphite. Red phosphorus is a crystalline and amorphous substance with a density of 2.0g/cm3. It is formed when white phosphorus is heated for several hours at a temperature of 530 kelvins (257 degrees Celsius). It is a highly flammable substance which burns red in oxygen. White phosphorus is the least amongst these three forms. It is the most reactive and very volatile. White phosphorus is also very poisonous (ChemSpider).

Reactions of Phosphorus

Phosphorus combines directly with very reactive metals such as sodium, potassium, and calcium to form compounds known as the phosphides. For example, a reaction between phosphorus and sodium produces sodium phosphide.

12Na(s) + P4(s) → 4Na3P(S)

The phosphides vigorously react with water to produce which is a gas and a hydroxide.

Ca3P2 (S) + 6H2O (l) → 2PH3(g) + 3Ca (OH)(aq)

The phosphides can also be prepared in the laboratory by reacting white phosphorus with a strong base.

P4(S) +3Na(OH)(aq) + 3H2O(l) → PH3 + 3NaH2

A reaction between phosphorus and halogen produces halides. However, when excess phosphorus is used with a halogen, a trihalide is formed.

P4(S) + 6Cl2(l) → PCl3

Phosphorus trichloride reacts violently with water to produce phosphoric acid and phosphorous acid (ChemSpider).

PCl3(l) +3H2O(l) → H3PO3(aq) +3HCl

PCl3(l) + 4H2O(l) → H3PO4(aq) + 5HCl

Formation of Oxides and Oxyacid

White phosphorus reacts directly with oxygen to produce two oxides depending on the amount of oxygen available. When excess phosphorus is used, phosphorus trioxide (P4O6(S)) is formed.

P4(S) +3O2(g) → P4O6(s)

Phosphorus pentoxide (P4O10(S)) is formed when there is excess oxygen.

P4(S) +5O2(g) → P4O10(s)

Phosphorus pentoxide and phosphorus trioxide react with water to form phosphorous acid and phosphoric acid respectively.

P4O6(s) + 6H2O(l) → 4H3PO3(aq)

P4O10(s) + 6H2O(l) → 4H3PO4(aq)

Importance of Phosphorus

Phosphorus is an important element in biological compounds. The teeth enamel is the hydroxyapatite Ca10(OH)2(PO4)(s) when there is no enough phosphorus in children’s diet, another substance which is much harder is formed. This substance, fluorapatite Ca10F10(PO4)6(s), is easily affected by acids (House).

The energy storing molecule the Adenosine Triphosphate (ATP) is a compound of phosphorus. Under the normal physiological conditions, one molecule of ATP is broken down to release out 31 Kilojoules of energy. The energy released is used by living cells to drive chemical reactions. The equation can be represented as follows:

ATP(aq) +H2O(l) → ADP + HPO42- + Energy

Adenosine diphosphate (ADP) is converted into ATP by the biochemical oxidation of food molecules. It is then availed to the muscles where it provides energy (House).

Phosphoric acid is one of the greatest important organic acids. It is widely produced and consumed in many countries. Phosphoric acid is used to manufacture fertilizers and feedstock. It is also used as food additive. Many detergents are made using phosphorus. Organic phosphates are also potent insecticides which when sprayed on plants, kills pests (House). Many paints are hardened using phosphorus. This enhances paint color, contrast, and durability. Phosphorus element is also very important in the manufacture of synthetic rubber. Genes which are hereditary are found in the cells are molecules of Deoxyribonucleic acid (DNA) which contains phosphorus.

Although phosphorus has a lower relative abundance compared to most elements on the earth surface. It is very essential for the life of both plants and animals. Life would be probably impossible without phosphorous.

References

Chemspider 2015. www.chemspider.com/Chemical-Structure.109894.html. Accessed on 6th December 2017.

House, J. E. (2013). Inorganic chemistry.

September 01, 2021

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