Phosphorus (P) – Uses & Chemical Properties

For thousands of years, the periodic table acknowledged the presence of phosphorus, but it was in 1669 that it was recognised as a separate element and given a name by the chemist Brandt. Due to its extreme reactiveness, the element phosphorus is not found freely in the atmosphere under normal circumstances. The atomic number of phosphorus is 15, meaning its atomic structure has 15 protons and 15 electrons. It is represented by the symbol P.

Atomic Mass of Phosphorus

Phosphorus has an atomic mass of about 30.973762 u. Atomic mass can be defined as the number of neutrons and protons an atom is composed of. The mass of each neutron and proton approximately equals one atomic mass unit. The mass of electrons in an atom is negligible as they are too tiny compared to neutrons and protons. The isotope of carbon called carbon-12, which is used as a standard, is composed of six neutrons and six protons. Therefore, its atomic mass is twelve amu.

Normally, the weight of an object depends on the gravitational force, unlike the atomic weight, which has nothing to do with it. It lacks a unit and can be defined as the ratio of the atomic masses of the element’s isotopes found in nature to 1/12th of the mass of carbon-12 isotopes. The atomic mass of elements like fluorine and beryllium is equal to their atomic weight as they have only one isotope that occurs in nature. 

The relative atomic mass of an element is calculated by determining the average atomic mass of its isotopes by keeping the carbon-12 isotope as a standard. 

Uses of Phosphorus

These days, four forms of phosphorus are generally used— black, white, violet, and red. The formation of teeth and bones is the main function of phosphorus. The use of phosphorus and plants is extensive as it is present in a variety of products like low phosphorus fertiliser, baking powder, and fireworks. It also has an important role to play in the manufacture of steel, fine chinaware, and special glasses. 

Health Effects of Phosphorus

Generally, phosphorus is found in the environment in the form of phosphates. Because these phosphates are part of DNA materials and contribute to energy delivery, they are essential substances in the human body. They can also commonly be found in phosphorus and plants. 

These days, phosphates are also added to several food products like sausages, cheese, and ham. Excessive levels of phosphates in food products can result in health problems like osteoporosis and kidney damage. On the other hand, too little phosphate can also cause health problems. 

In its pure form, phosphorus is white in colour. It is the most toxic source of phosphorus known. Excess amounts of white phosphorus in nature can pose serious health risks. It is extremely dangerous and can even be fatal.

Properties of Phosphorus

Phosphorus is a multivalent nonmetal that belongs to the nitrogen group of the periodic table. It can be found in several allotropic forms in nature and is essential for the life of organisms on Earth. Phosphorus is found in several forms— black, red, and white. White phosphorus is manufactured in the industry; it is fluorescent, extremely toxic, and flammable on exposure to air. The colour of red phosphorus can vary from orange to purple because of slight variations in its chemical structure. Black phosphorus, the third form, appears similar to graphite and is manufactured under high pressure. It can also conduct electricity like graphite. 

Applications of Phosphorus

Phosphoric acids in concentrated forms are used to manufacture low phosphorus fertiliser for farms and agriculture. Phosphates are employed in the production of sodium lamps, special glasses, military applications, and in steel production and pesticides, pyrotechnics, detergents, and toothpaste.

Phosphorus in the Environment

Phosphorus is never encountered in its pure form in nature. It can only be found as phosphates which comprise a phosphorus atom attached to four atoms of oxygen. It is usually found as a phosphate ion that is negatively charged PO₄^3- It is also found in minerals in the phosphate ion form or as organophosphates. The organophosphate form contains organic molecules bonded to one, two, or three atoms of oxygen.

The phosphorus content occurs in varying amounts in food products. In the liver, it can be as high as 370 mg/100 g, while in vegetable oil, it can be quite low. Examples of phosphorus-rich foods include salmon, liver, tuna, sardines, turkey, eggs, chicken, and cheese. 

Many phosphate minerals exist, of which the most abundant form is apatite. Most extensive mined deposits are provided by fluorapatite. Russia, Morocco, the USA, Togo, Tunisia, and Nauru are the prime mining areas. Annually, the world’s production of phosphates is around 153 million tons. However, how long these phosphorus deposits will last is concerning. If they were depleted, the food production in the world would be impacted seriously as it is a very important ingredient in low phosphorus fertiliser.

The concentration of phosphates in the oceans is quite low, especially on their surfaces. The main reason is that they are insoluble in calcium and aluminium phosphates. But usually, the phosphates in the oceans are quickly exhausted, and they drop deep, forming organic debris. More phosphate content may be present in lakes and rivers, increasing the growth of algae. 

Health Effects of Phosphorus 

As discussed earlier, phosphates are most commonly found in the environment as phosphates. As phosphates are parts of DNA materials in the body and take part in energy distribution, they are vital substances in the human body. 

Phosphate is required in the diet, having an RDA of around 800 mg/day. Around 1000-2000 mg/dl of phosphate is provided per day by a normal diet, depending on the amount of phosphate-rich foods consumed.

Too much phosphate is detrimental to health. Most cases where people have died due to exposure to white phosphorus involved accidental ingestion of rat poison. Before dying, these people usually experience stomach cramps, nausea, and drowsiness. White phosphorus can lead to skin burns associated with liver or kidney damage. 

Environmental Effects of Phosphorus

White phosphorus content increases in the environment when it is utilised in industries for the manufacture of other chemicals or when it is used in ammunition. It enters the surface of water bodies by discharging wastewater from nearby factories.

As white phosphorus reacts with oxygen quite fairly, it is not prone to spreading. When it ends up in the atmosphere through exhausts, it usually reacts with oxygen quickly to be changed into less toxic substances. However, when in the air, phosphorus particles may be protected from chemical reactions by a protective coating.

White phosphorus does not react with other particles in water rapidly; therefore, it accumulates in the bodies of aquatic organisms. Phosphorus stays in the soil for several days before getting converted to less harmful substances. However, in deep soils and river and lake bottoms, phosphorus in plants may stay for even a thousand years. 

Effects of Phosphates

Phosphates affect organisms in many different ways, most of which are consequences of the emissions of high amounts of phosphates into the air as a result of mining and cultivating. Phosphates are often not removed properly during water purification, so they tend to spread over long distances when they occur on water surfaces. 

Because of the excessive phosphate content in nature and constant addition by humans, there has been a strong disruption of the phosphorus cycle. Due to the increasing phosphorus concentrations on the surface of the water, there has been an increase in the growth of organisms that depend on phosphates, like duckweed and algae. These organisms consume considerable amounts of oxygen and prevent the entering of sunlight into the water, making it unfavourable for other forms of life. This phenomenon is generally referred to as eutrophication.

Conclusion

We hope that this blog helped you gain a fundamental understanding of the element phosphorus. You can check out our other blogs to learn about other elements of the periodic table.

Frequently Asked Questions

1. What is phosphorus used for?

Phosphorus is an important plant nutrient. The main use of phosphorus and plants is in producing fertilisers. Apart from the bicarbonate and nitrogen cycles, there is also a phosphorus cycle that occurs in nature. Red phosphorus is employed in producing safety matches, inflammatory shells, and pyrotechnics.

2. What is unique about phosphorus?

Most forms of phosphorus do not conduct heat and electricity effectively, but almost all of the forms are stable at room temperature. White phosphorus appears similar to wax, the purple and red forms are non-crystalline solids, and the black form is similar to graphite which is seen in pencil leads. 

3. What are the main sources of phosphorus?

A considerable amount of phosphorus is found in protein foods like milk and milk products. It is also found in nuts, lentils, beans, whole grains, and meat. Fruits and vegetables also contain phosphorus in small amounts.