The Story of Iodine

One day in 1811, French chemist  Bernard Courtois was trying to extract potassium chloride from seaweed. After crystalizing the potassium chloride, he added sulfuric acid to the rest of the liquid. This resulted in a purple vapor which condensed into dark crystals, thus the birth of Iodine. Once discovered, Bernard (the “father” of Iodine) made a biography about his “son”, named Iodine; deriving his son’s name from the Greek word: iodes, meaning violet.

Biography of Iodine, born 1811

  1. 1.    Appearance and Properties 

–  Bluish black and a lustrous (or shiny) solid.

–  Vaporizes at room temperature into a blue-violet gas with an irritating smell

–  Possesses some metallic-like properties, even if it’s a non-metal; i.e. it’s shine

–  Dissolves readily in chloroform, carbon, tetrachloride, or carbon disulfide to form purple solutions.

–  Only slightly soluble in water

  1. 3.   Unique Features:

–  Iodine occurs naturally in the form of iodine ions, mainly in seawater. It’s introduced to humans via the food chain when consuming seaweed and other sea-plants.

  1. 4.    Applications:

–  Iodine is used in medicine, in both reactive and non-radioactive forms.

–  It can be used as a disinfectant before medical procedures are carried out.

–  It also is used in curing thyroid cancer.

Next, iodine has a special biography, in terms of chemical properties. These can be seen below:

Chemical Property


In the context of Iodine

Atomic Number

Number of protons in the nucleus of an atom


Atomic Mass

Mass of an atom of a chemical element expressed in atomic mass units.


Melting Point

The temperature wherein a certain solid will melt.


Boiling Point

The temperature where a liquid boils and turns to vapor.



The property of being metallic


Shielding Effect

The Shielding Effect is the effect where core electrons block valence electrons from the nuclear charge of the nucleus.


Ionization Energy

This is the energy required to remove the outermost electrons from a gaseous atom. 1008.4 kJ mol-1, 1845.8 kJ mol-1, 3184 kJ mol-1

Atomic Radius

It is used to describe the size of the atom. It may refer to covalent radius, metallic radius, or van der Waals radius.

140 pm

Ionic Radius

It is the distance between the center of the nucleus and the outer edge of the ion (measured in picometers)

206 pm (1- ion)


Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

Based on the Pauling Scale: 2.66

Nuclear Charge

This is the total charge if all the protons in the nucleus.

1s- 51.94; 2s- 39.07; 2p- 48.85; 3s: 34.79; 3p: 34.84; 3d: 38.90; 4s: 25.30;  4p: 24.03; 4d: 20.93; 5s: 13.40; 5p: 11.61

Valence Electrons

Valence electrons are the electrons in the last shell or energy level






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