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Iodide Formula – Structure, Properties, Uses, Sample Questions

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  • Last Updated : 01 Mar, 2023
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Iodine is a chemical element with symbol I and atomic number 53.The heaviest of the stable halogens. It is the fourth halogen being a member of group 17 in the periodic table. It is a trace element that is  naturally present in some foods. The body needs iodine to make thyroid hormones. These hormones control the body’s metabolism. It is founded mainly on animal protein foods and sea vegetables and to a lesser extent on fortified foods like bread, cereals, and milk. Its salts are used in pharmaceuticals and disinfectants, printing inks and dyes, animal catalysts, feed supplements, and chemicals in photography.


An iodide ion is an ion I-[2] compound with iodine. Iodide salts are defined as mild reducing agents, and several reacts with oxygen to form iodine. In every day life it is mostly used as a component of iodized salt. It is one of the largest monatomic anions.

Formula Of Iodide

The chemical iodide formula is I. Iodine has an electron configuration of [Kr]4d10 5s2 5p5 .It has seven valency electrons in the fifth and outermost shell. It is one electron short of a full octet and is, therefore, an oxidizing agent reacting with many other elements in order to complete the outer shell; however, in keeping with periodic trends, it is the weakest oxidizing agent among the stable halogens it has the lowest electronegativity among them. Simply the iodide ion I is the strongest reducing agent among the stable halogens, being the most easily oxidizing back to diatomic I2.

Structure Of Iodide


In this structure, to draw the structure for iodide ions, first, we write the structure of iodine. Iodine is a chemical element with the symbol I. Its belongs to 17th  group of the periodic table, and it has seven valency electrons .neutral iodine doesn’t have any charge. But iodide has a negative charge.Such it has a negative charge, then it has one extra electron, then it has a total of eight valency electrons, and that means it is very stable . It gains the electron that’s why it has a negative charge Iodide ion.

Physical Properties Of Iodide

  • Iodide molecular weight is 126.904 g/mol
  • Its density is 3.13 g/cm3
  • Its boiling point is 184.3°C
  • Its melting point is 113.7°C

Chemical Properties Of Iodide

  • Iodide chemical formula is I
  • It is soluble in water 
  • Iodide compounds sodium salt reacts with lead nitrate and produces sodium nitrate and lead iodide.                    

Pb(NO3)2 + 2 NaI ⇢ 2 NaNO3 + PbI2

  • Potassium Iodide salt combines with chlorine to produce iodine and potassium chloride.                                                  

2 KI + Cl2 ⇢ 2KCl + I2

Harmful Effects Of Iodide 

  • The excess intake of iodide can inhibit the synthesis and release of thyroid hormone resulting in goiter and hypothyroidism.
  • It can cause burning in the mouth. 
  • Irregular heartbeat.
  • Soreness of teeth and gums.
  • Stomach upset.

Safety Measures for Iodide

  • Avoid contact with skin and eyes.
  • Wear protective safety glasses.
  • Avoid inhalation.
  • Ingestion May be harmful if swallowed.
  • Flush eyes with water.
  • Get medical attention immediately if irritation persists.

Uses Of Iodide

  • Iodide salts are used in printing inks and dyes.
  • It is used as an animal feed supplement and photographic chemicals.
  • Its compounds like potassium iodide are used to protect the thyroid gland from possible radiation injury caused by radioactive iodine.
  • It is used to disinfect the skin before surgery. 
  • It has disinfectant property and is not readily affected as chlorine by water pH or organic content, but iodide disinfectant activity is markedly  reduced by cold water temperature.

Sample Questions

Question 1: What is the difference between iodine and iodide?


Iodine with symbol I and atomic number 53. It is the heaviest of the stable halogens. It is the fourth halogen being a member of group 17 in the periodic table. However, the molecular form consists of two atoms of iodine stuck together . Iodide is a salt that could, for example, be combined with calcium or potassium and can be found in seaweed sources and mineral deposits.

Question 2: Iodine found in which foods?


Iodine is founded mainly on animal protein foods and sea vegetables and to a lesser extent on fortified foods like bread cereals and milk, and it is available in dairy products, seaweed, eggs, beef liver, and chicken also.

Question 3: Does milk have iodine?


One can get recommended amounts of iodine by eating a variety of foods. Dairy products are major sources of iodine. The consumption of milk and dairy products along with their iodine concentrations vary widely, making them an unpredictable iodine source.

Question 4: Is iodide metal or non metal?


It is a nonmetal. It exhibits some metallic qualities. Iodine is classified as a halogen. It is a subset of very chemically reactive elements that exist in the environment as compounds rather than as pure elements.

Question 5: Is iodide soluble in water?


The iodide salts are soluble in water. Iodide, being large, is less hydrophilic compared to the smaller anions. Sodium iodide is highly soluble in acetone, whereas sodium chloride is not.

Question 6: Is iodide a good nucleophile?


Yes, Iodide is a good nucleophile because of its bigger size and lower electronegativity. The lack of basicity of the iodide anion relatively in water is precisely that makes it a good nucleophile.

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