[Chemistry Class Notes] on Phosphorus Pdf for Exam

Phosphorus is a chemical element that represents symbol (P) and has phosphorus atomic number 15. It exists in two primary forms, i.e., red phosphorus and white phosphorus. It is highly reactive in nature; therefore, it is never found as a free element on earth. In the earth’s crust, its concentration is about one gram per kilogram. Phosphorus is usually known as ‘phosphate’ in minerals. Here are some facts about Phosphorus –

• Group = 15

• Period = 3

• Block = p

• Atomic number = 15

• State at 20 degrees = Solid

• Electron configuration = [Ne] 3s23p3

• ChemSpider ID = 4575369

• Melting point = 44.15°C

• Boiling point = 280.5°C

• Density = 1.823 gm cm-3

• Relative atomic mass = 30.974

• Key isotopes = 31p

History of Phosphorus

Hennig Brand discovered phosphorus in the year 1669. Hennig was a German merchant whose hobby was alchemy. He allowed around 50 buckets of urine to stand until they purified and bred worms. Brand thereby discovered distilling elemental phosphorus from the mixture by boiling the urine into a paste and then heating it with sand. He reported his discovery and demonstration in a letter, along with the ability of the element to glow in the dark, otherwise known as ‘Phosphoresce’ which excited public interest. After a century, phosphorus proved to be a component of bones. Phosphoric acid is the digestion of bones with sulfuric and nitric acid from which phosphorus is distilled by heating charcoal.

The Chemical Appearance of Phosphorus

The main types of phosphorus are white and red phosphorus. While the nature of white phosphorus is poisonous solid waxy and contact with the skin can cause severe burns. It can glow in the dark and is instantly flammable when exposed to air. Red phosphorus in nature is an amorphous non-toxic solid.

Uses of Phosphorus

There are many phosphorus uses, among which white phosphorus is used in incendiary devices and flares. In everyday use, red phosphorus is found on the side of the matchbox. Safety matches are struck against it to light them. 

 

The significant use of the phosphorus compound is for fertilisers. Phosphate ores are created from ammonium phosphate. The ores are initially converted into phosphoric acid before being converted into ammonium phosphate.

 

Phosphorus is also a vital element in the production of steel. Some detergents have phosphate as an ingredient, but it has started to phase out in several countries. Due to high phosphate level in natural water supplies, it can cause unwanted algae to grow. The production of fine chinaware and special glasses also uses phosphates.

Uses of Phosphorus for Health and Body

Phosphorus is a mineral that is found in foods like beans, fish, cheese, and beer. It is a common substance in the everyday environment of your body. It plays a crucial role in the bones, muscles, kidneys, and blood vessel health along with the cells in your body.

 

Along with calcium, phosphorus helps build bones. For good bone health, you need a correct amount of calcium as well as phosphorus. Phosphorus is a vital structure in nucleic acids and cell membranes and is also involved in the production of the body’s energy. When the level of calcium is high, your body absorbs less phosphorus and vice versa. Also, vitamin D is essential to absorb phosphorus properly.

 

You can get the right amount of phosphorus and maintain the balance. For lowering the levels of phosphorus, medical practitioners may prescribe phosphate binders. By consuming the binders with meals and snacks, it limits the amount of phosphorus your body can absorb. Various lifestyle choices like staying hydrated, enough exercising, and having a balanced low phosphorus diet can balance the levels of phosphorus.

Foods That Have a High Level of Phosphorus are as Follows:

Foods Too Low on Phosphorus are as Follows:

• Vegetables

• Fresh fruits

• Popcorn

• Saltines

• Bread

• Cornflakes

• Eggs

Physical Properties of Phosphorus

Physical properties are the characteristics that can be seen without changing the substance into another substance. Physical properties are observed using senses like colour, boiling point, freezing point, melting point, hardness, density, and odour. 

The Physical Properties are as Follows:

• White phosphorus is a poisonous waxy solid which emits a greenish-white glow. It glows in the dark and is instantly flammable when exposed to air. Also, it does not dissolve in water.

• Red phosphorus is in the form of a powder that can vary in colour from purple to orange because of the minimal variation in chemical structure. It does not dissolve in various liquids.

• Black phosphorus is formed under high pressure which looks more like graphite powder and can conduct electricity.

Chemical Properties of Phosphorus

Chemical properties are the characteristics that determine their reaction with another substance or its ability to change from one element to another. Only during a chemical reaction, chemical properties are observed.

• Most of the chemical activity is exhibited by white phosphorus

• Red and black phosphorus are passive n chemical reaction

• Through a chain reaction, the oxidation of white phosphorus occurs

• Combines directly with all halogens

• Phosphorus forms phosphides when heated with metal

Types of Phosphorus

Let us take a look at the different type of phosphorus. The two main forms of phosphorus are red and white phosphorus. 

1. White Phosphorus: White phosphorus is the least stable, most volatile, most reactive, the least dense, and the most toxic allotrope of all. White phosphorus is capable of gradually changing to red phosphorus. The transformation is caused by lig
   ht and heat. The samples of the white phosphorus always consist of some red phosphorus and appear yellow in color. When exposed to oxygen, the white phosphorus is capable of glowing in the dark by illuminating a tinge of green and blue color. On reacting with air, it is highly flammable and pyrophoric upon contact. Owing to its property of pyrophoricity, white phosphorus is used as an additive. The odour of combustion has a characteristic to smell like garlic, and the samples are commonly coated with white “phosphorus pentoxide”.

2. Red Phosphorus: Red phosphorus is a polymeric structure. It can be viewed as a derivative of P4 whereas one of the P-P bonds is broken. One of the additional bonds is formed with the neighbouring tetrahedron atom that results to form a chain-like structure. Red phosphorus may be formed by heating white phosphorus at 250 0C. It can also be formed by exposing the white phosphorus to the sunlight. After this treatment phosphorus is amorphous in nature. On further heating, this material can crystallize. By this, we can tell that the red phosphorus is not an allotrope, but it acts as an intermediate phase in between the white and violet phosphorus. Most of the properties have a different range of values. 

Difference Between Red and White Phosphorus

Allotropes of Phosphorus

Phosphorus has several allotropes that are capable of exhibiting diverse properties. The structure of P4 molecules are determined by the gas electron diffraction. From the perspective of the application, the required form of elemental phosphorus is white phosphorus. It is a soft, waxy solid which contains tetrahedral P4 molecules, in which each of the atoms is bound to the remaining three atoms by a single bond. This P4 tetrahedron is also present in liquid and gaseous forms of phosphorus. 

• White phosphorus can exist in two other crystalline forms such as alpha and beta forms. At room temperature, the alpha form is stable. It is the more common form and it has a cubic crystal structure and it transforms into beta form 195.2 K. This beta form has a hexagonal crystal structure. These forms differ in terms of the relative orientations of the constituent P4 tetrahedra.

• Violet phosphorus is another form of phosphorus that can be produced by the process of annealing the red phosphorus above the temperature of 5500C. In the year 1865, a scientist named Hittorf discovered that phosphorus was recrystallized from the molten lead to get a red or purple form of phosphorus. Therefore, this form is known as “Hittorf’s phosphorus” or violet phosphorus or –metallic phosphorus.

• Phosphorus black is the least reactive allotrope and it will be in a thermodynamically stable form. It is also known as –metallic phosphorus. The structure somewhat resembles that of the graphite. This form can be obtained by heating the white phosphorus under the condition of high pressure. It can also be formed at ambient conditions using metal salts such as mercury, as catalysts. In all the characteristics such as physical and chemical properties, appearance, and structure, it resembles graphite. Since it is black and flaky, it acts as a good conductor of electricity and has tightly packed sheets of linked atoms.

Compounds of Phosphorus

• Phosphorus (V): The compounds of phosphorus that are prevalent are derivatives of phosphate (PO43 –) which is a tetrahedral anion. Phosphate acts as a conjugate base for the phosphoric acid, which is manufactured on a large scale for use in fertilizers. 

Since it is triprotic in nature, phosphoric acid gets converted stepwise to form into three conjugate bases: 

• Phosphate exhibits a tendency to form chains and rings that contain P – O – P bonds. Many of the polyphosphates are known and used frequently, this includes ATP as well. Polyphosphates that arise by the process of dehydration of the hydrogen phosphates such as HPO42- and H2PO4–. For example, the industrially important Penta-sodium triphosphate which is also known as sodium tripolyphosphate, STPP is produced by condensation reaction.

• Phosphorus pentoxide is the anhydride form as the phosphoric acid, but most of the intermediates that are present in between these two are known. This waxy white solid is capable of reacting vigorously with water. 

• Along with the metal cations, the phosphate can form a variety of types of salts. These solids are polymeric in nature and contain P-O-M linkages. When the metal cation has a charge of 2+or 3+ then those salts are generally insoluble thus these can exist in the form of common minerals.

• PCl5 and PF5 are the commonly found compounds. PF5 is a colorless gas and molecule that exhibits trigonal bipyramidal geometry. PCl5 is a colorless solid which has an ionic formulation of PCl4+ PCl6–, but it can adopt the trigonal bipyramidal ge
  ometry when it is molten or in the vapor phase. PBr5 is an unstable solid that is formulated as PBr5+ Br –and PI5 is not known. The pentachloride and pentafluoride are Lewis acids. 

• Phosphorus(III): All four symmetrical trihalides are known as gaseous PF3, the yellowish liquids are PCl3and PBr3, and the solid is PI3. These materials are sensitive to moisture, and they hydrolyze to make phosphorous acid. The trichloride is a common reagent that is produced by chlorination of white phosphorus:

P4+6Cl2 → 4PCl3

The trifluoride is manufactured from the trichloride by the process of halide exchange. The PF3is toxic in nature because it can bind to the hemoglobin.

• Phosphorus(I) and phosphorus(II): These are the compounds that generally have P–P bonds. Some of the examples include catenated derivatives of phosphine and organophosphines. Compounds containing P=P double bonds have also been observed, although they are rare.

• Phosphides and Phosphines: Phosphides arise from the reaction of metals with red phosphorus. The alkali metals and alkaline earth metals can form ionic compounds containing the phosphide ion. These compounds can react with the water to form phosphine. With the transition metals as well as the monophosphides, there are metal-rich phosphides, which are generally hard refractory compounds with a metallic luster, and phosphorus-rich phosphides which are less stable and include semiconductors. Schreibersite is a naturally occurring metal-rich phosphide found in meteorites. The structures of the metal-rich and phosphorus-rich phosphides can be complex.

• Oxoacids: Phosphorus oxoacids are extensive, often commercially important, and sometimes these are structurally complicated. They all have acidic protons that are bound to the oxygen atoms, some of these have non-acidic protons that are directly to phosphorus. Some of these contain phosphorus-phosphorus bonds. Although many of the oxoacids of phosphorus are formed, among them only nine are commercially important. Where three of them are phosphorous acid, hypophosphorous acid, and phosphoric acid, these are particularly important.

Conclusion

Organic compounds that are produced from phosphorus forms a wide variety of materials. Among these many of them are required for life, but some of them are extremely toxic. Fluorophosphate esters are the most known among the most potent neurotoxins. Due to their toxicity a wide range of organophosphorus compounds are used as pesticides and as nerve agents against human enemies. Most inorganic phosphates are relatively essential nutrients and they are non-toxic in nature. The allotrope white phosphorus is present as a significant hazard because it can ignite in the presence of air and produces residues of phosphoric acid. The poisoning of Chronic white phosphorus leads to the causing of necrosis of the jaw called “phossy jaw”. White phosphorus is toxic in nature, it causes severe liver damage on ingestion and may cause a condition known as “Smoking Stool Syndrome”.