Phosphorus | No. of valence electrons in it?

In this blog we will determine the number of valence electrons in phosphorus atom. This blog will provide you detailed information about phosphorus and it’s valence electrons. We will also discuss it’s properties, applications and some disadvantages. After exploring this blog, you will be able to know some basics and a detailed overview of phosphorus. Let’s start by discuss ing history and discovery of phosphorus.

History and discovery of phosphorus

The word phosphorus is derived from the Greek word  (φῶς = light, φέρω = carry) which means light carrier.

It was initially discovered in 1669 by a German chemist Henning Brand. He took an experiment with urine. He attempted to create the fabled philosopher’s stone through the distillation of some salts by evaporating urine. In this experiment Brand got a white material which was glowing in the dark and burned nicely. It was named as phosphorus mirabilis.

In 1680 Robert Boyle was the first man who use phosphorus to ignite sulphur-tipped wooden splints.

Later on in 1777, it was acknowledged as element by Antoine Lavoisier.


Phosphorus is an element present in group 15 (5A) and in third period with the symbol P, atomic number 15 and atomic mass 30.973. There are two major forms of phosphorus, white phosphorus and red phosphorus. Phosphorus is not found freely in nature because it is highly reactive.

How we can determine the valence electrons in Phosphorus?

We can use two methods to determine valence electrons in phosphorus atom.

  1. Determining with the help of periodic table
  2. Determining by it’s electronic configuration

Determining with the help of periodic table

As we can see Phosphorus lies in group 15 (also called as group 5A). As every element present in this group will have five valence electrons, phosphorus will also have five valence electrons. . Atomic number of phosphorus is 15 which means it has 15 protons since these all are neutral, number of protons is equal to the number of electrons (15). Atomic mass of phosphorus is 30.97.

Determining by it’s electronic configuration

electronic configuration of phosphorus

Electronic configuration of phosphorus is: 1s2, 2s2, 2p6, 3s2, 3p3. The outermost orbitals are 3s2, sp3. These outermost orbitals contain 5 electrons (2+3=5 electrons). So, it has 5 valence electrons.

Describe some Properties of Phosphorus?

  • It is highly reactive element.
  • White phosphorus is very poisonous and it can spontaneously combust in air.
  • Phosphorus can form different compounds like: phosphorus acid, phosphoric acid and phosphates.
  • It’s 15 atomic number is 15 and atomic mass is 30.973 (31).
  • It can appear in white, red and violet colors.
  • Boiling point of phosphorus is 553.7 K and melting point is 317.3 K.
  • Heat of fusion of phosphorus is 0.66 KJ/mol.
  • Heat of vaporization of phosphorus is 51.9 KJ/mol.
  • Phosphorus has different density values for white, red, violet and black phosphorus and these values are 1.823 g/cm3, 2.2 g/cm3, 2.36 g/cm3, 2.69 g/cm3 respectively.
  • Electronegativity of phosphorus is 2.19 on Pauling scale.
  • Phosphorus have body centered cubic crystal structure.
  • There are three main isotopes of phosphorus 31P, 32P, 33P. 31P is most stable among all of these.

Write some uses of Phosphorus?

  • Phosphorus is very essential to life.
  • Most of our phosphorus comes from phosphate rock and then converted into phosphoric acid. Approximately Fifty million tones are made every year and it is used in multiple fields.
  • It is used to make animal feeds.
  • It is also used in making rust removers, corrosion preventers and dishwasher tablets.
  • Each molecule of DNA and RNA contains major part of phosphorus.
  • Side of matchboxes are made up with red phosphorus.
  • Phosphorus is present in bones. Phosphorus is used in fertilizers.
  • It is the 6th most common element in human body.
  • It is the seventh most common element in the earth’s crust.
  • It is used in fertilizer industry.
  • Phosphorus compounds are also used in chemical industry for applications in soft drinks, flame retardants and pharmaceuticals .
  • Phosphorus as a mineral makes 1% of the person’s total body weight.
  • It is needed for the body to make protein for the growth, maintenance and repair of cells and tissues.
  • Phosphorus works with vitamin B.

Disadvantages/negative effects of Phosphorus

  • Too much use of phosphorus and phosphates in environment leads towards algae to bloom in rivers and lakes. The excess algae uses up all the dissolved oxygen in the water and fish dies.
  • Early on, Phosphorus was used in the match head. By overexposing to phosphorus, workers in match factories were developed a painful and debilitating deformation of jawbone known as phossy jaw.
  • It is highly reactive and can cause damage.
  • The white phosphorus is deadly poisonous.
  • Access of phosphorus/phosphate in the body can cause diarrhea.
  • High phosphate level promotes the progression of kidney disease.
  • Excessive soil phosphorus reduces the plant’s ability to take up required micronutrients.
  • High phosphorus will interfare with nitrogen absorption, so the plant will lack growth in it’s stem and foliage, causing a stunted growth.


Phosphorus have five valence electrons, as we have determined it. It is an element present in group 15 (5A) with 15 atomic number represented by P symbol. By having five valence and 15 total electrons, It’s electronic configuration is 1s2, 2s2, 2p6, 3s2, 3p3. Different compounds like: phosphorus acid, phosphoric acid and phosphates can be formed from phosphorus. It possesses three main isotopes. Phosphorus has many uses/applications in daily life, in human body, in fertilizers, in pharmaceuticals and in plants.

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