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Phosphorus

What is Phosphorus

Phosphorus (pronunciation: FOS-fer-es) is a highly-reactive element classified as a non-metal represented by the chemical symbol P [1, 2, 3]. It mainly exists in its two allotropic forms, including the waxy, white solid and the non-crystalline, solid red that is obtained by heating white phosphorus [3, 4, 5].

Isotopes

There are 24 isotopes of phosphorus, ranging from 24P to 47P out of which 31P is stable [6]. While most of the radioactive isotopes are short-lived with half-life periods less than 2.5 minutes, 33P and 32P are the longest-lived with half-lives of 25.34 days and 14.263 days respectively [6]. The least stable among the 24 isotopes of 15P is 25P characterized by a half-life period less than 30 nanoseconds [6].

Phosphorus

Where is Phosphorus Found

Phosphorus does not occur freely in nature, but it forms compounds with other elements in minerals [1]. It is mainly obtained from phosphate rock, including the apatite phosphate mineral [1].

White phosphorus is commercially produced by treating phosphate rock with silica and carbon in a fuel-fired or electric furnace [1]. Phosphorus is produced as a vapor, which is collected under water [1]. Red phosphorus is manufactured by heating the white form to 250 °C in an inert atmosphere [1].

The top 3 phosphorus producing countries are China, Mexico, and Morocco while the top 3 phosphorus reserve holders include Morocco, China, and the USA [1].

Phosphorus Symbol

History

Origin of its Name: It is derived from ‘phosphoros’, Greek for the bringer of light [1]

Who discovered it: The element was discovered by the German merchant and alchemist Hennig Brand [1, 2].

When and How was it Discovered

In 1669, Hennig Brand discovered phosphorus at Hamburg by boiling urine and then heating the residue, which produced phosphorus vapor [1]. Then, he distilled the phosphorus vapor and collected it after condensing it in the water [1]. Hennig Brand decided to keep his discovery secret because he thought that he had produced the Philosopher’s Stone which could be used for turning metals into gold [1].

Since Hennig needed money, he sold it to Daniel Kraft who displayed it around Europe, capturing the attention of Robert Boyle [1]. He studied phosphorus systematically and found out its characteristics [1].

White Phosphorus

Phosphorus Identification

Atomic number 15 [1]
CAS number 7723-14-0 [1]
Position in the periodic table Group Period Block
  15 [1] 3 [1] p [1]

Properties and Characteristics of Phosphorus

General Properties

Relative atomic mass 30.974 [1]
Atomic mass 30.974 amu [1]
Molar mass 30.9737620 ± 0.0000020 g/mol [7]
Molecular weight 30.974 g/mol [3]
Allotropes White (yellow), Red, Black [1]

Physical Properties

Color Usually, white or pale yellow [5]
Melting point/freezing point 44.15 °C, 111.47 °F [1]
Boiling point 280.5 °C, 536.9 °F [1]
Density 1.823 g cm-3 (white) [1]
State of matter at room temperature (solid/liquid/gas) Solid [1, 5]
Electrical Conductivity 1 X 107 S/m [8]
Charge -3 [9]
Thermal (heat) conductivity 0.236 W/(m K) [8]
Specific heat 769 J kg-1 K-1 [1]
Bulk modulus 10.9 GPa (red), 4.9 GPa (white) [1]
Shear modulus Unknown [1]
Young’s modulus Unknown [1]
Vapor pressure
– Temperature (K) 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
– Pressure (Pa)

Chemical Properties

Oxidation states 5, 3, -3 [1]
Isotopes Isotope Mass Abundance (%) Half-life Mode of decay
  31P 30.974 100

Orbital Diagram for Phosphorus

Atomic Data of Phosphorus (Element 15)

Valence electrons 5 [10]
Quantum numbers
– n 3 [10]
– ℓ 1 [10]
– m 1 [10]
– ms +1/2 [10]
Electron configuration (noble gas configuration) [Ne] 3s23p3 [1]
Atomic structure
– Number of electrons 15 [11]
– Number of neutrons 16 [11]
– Number of protons 15 [11]
Radius of Atom
– Atomic radius 1.80 Å [1]
– Covalent radius 1.09 Å [1]
Electronegativity (Pauling-scale) 2.19 [1]
Electron affinity 72.037 [1]
Ionization energy (kJ mol-1) 1st 2nd 3rd 4th 5th 6th 7th 8th
  1011.812 1907.467 2914.118 4963.582 6273.969 21267.395 25430.64 29871.9

Phosphorus Electron Configuration (Bohr Model)

What is Phosphorus Used for

  • Its allotropic white form is used in incendiary bombs and flares [1].
  • Red phosphorus is used in manufacturing safety matches and is stuck on the matchboxes so that the matches can be lit by striking against them [1, 5].
  • Phosphorus compounds are generally used in fertilizers [1, 5].
  • Phosphate ores are an important source of ammonium phosphate [1]. The ores are converted into phosphoric acids and then into ammonium phosphate [1].
  • It is also an essential ingredient in the manufacture of steel, phosphor bronze, and some detergents [1, 5]. However, its use in detergents has now been phased out in several countries because it can accumulate in natural water supplies and induce the growth of unwanted algae [1].
  • It is used in manufacturing fine chinaware and special glasses [1].
  • Phosphorus is one of the materials used for producing LEDs (light-emitting diodes) [5].

Red Phosphorus

Toxicity and Health Effects

An excess of phosphate in the human body can cause soft tissue, hardening of organs, or diarrhea [12]. It can also affect your body’s mechanism of utilizing other essential minerals like zinc, calcium, magnesium, and iron [12].

While too much phosphorus is toxic for your health, too little of it can weaken your teeth and bones, as well as cause anxiety, fatigue, and loss of appetite [12].

It is an essential nutrient for plants, which help in moving it through the biosphere, lithosphere, and hydrosphere and this cycle is known as the phosphorus cycle [5].

Phosphorus Cycle

Interesting Facts

  • The average amount of phosphates in the human body, mostly in the teeth and bones, is estimated at 750 g (26.5 ounces) [4].
  • A 2013 study has shown that the phosphorus in the Earth’s crust may have been brought by meteorites [4].
  • High phosphorus levels in the blood is a warning sign for heart diseases [4].
  • Since white phosphorus exists as molecules consisting of four atoms arranged in a tetrahedral structure, its graphical representation indicates this tetrahedral shape with a ball-and-stick model [1].

Cost of Phosphorus

The price of pure phosphorus is $0.3 per gram [5].

References

  1. http://www.rsc.org/periodic-table/element/15/phosphorus
  2. https://education.jlab.org/itselemental/ele015.html
  3. https://pubchem.ncbi.nlm.nih.gov/compound/5462309#section=Top
  4. https://www.livescience.com/28932-phosphorus.html
  5. https://www.chemicool.com/elements/phosphorus.html
  6. https://education.jlab.org/itselemental/iso015.html
  7. https://www.webqc.org/molecular-weight-of-Phosphorus.html
  8. http://periodictable.com/Elements/015/data.html
  9. http://www.cabrillo.edu/~aromero/Common%20Files/Periodic%20Table%20(Common%20Ionic%20Charges).pdf
  10. http://chemistry-reference.com/q_elements.asp?Symbol=P
  11. https://hobart.k12.in.us/ksms/PeriodicTable/phosphorus.htm
  12. https://www.healthline.com/health/phosphorus-in-diet#toomuch-phosphorus

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