Difference Between Iodine and Iodide

The key difference between iodine and iodide is that the iodine is a chemical element whereas the iodide is an anion.

We can understand the iodine and iodide variation very easily if one has a basic understanding of chemistry. But, there are many who confuse with the two terms and use the two words interchangeably, which is not correct. Iodine is a chemical compound that is purple in colour whereas iodide is an ion and cannot remain in free state implying it has to combine with another element or elements to form a compound. Hence, iodine is an element with high atomic number 53, and we can represent it by the symbol I whereas iodide being an ion and is represented by 1-.

CONTENTS

1. Overview and Key Difference
2. What is Iodine
3. What is Iodide
4. Side by Side Comparison – Iodine vs Iodide in Tabular Form
5. Summary

What is Iodine?

Iodine is a chemical element having the atomic number 53 and chemical symbol I. It is the heaviest halogen (halogens are group 17 chemical elements in the periodic table). Also, this element exists in a solid state at room temperature. It has a lustrous, metallic-grey appearance. Furthermore, this compound readily undergoes sublimation to form the violet gas of iodine.

Moreover, there are many oxidation states that iodine can exist. However, the -1 oxidation is the most common among them, which results in the iodide anion. Some chemical facts about iodine are as follows:

• Atomic number – 53
• Standard atomic weight – 126.9
• Appearance – lustrous, metallic-grey solid
• Electron configuration – [Kr] 4d¹⁰ 5s² 5p⁵
• Group – 17
• Period – 5
• Chemical category – nonmetal
• Melting point – 113.7 °C
• Boiling point – 184.3 °C

Above all, iodine is a strong oxidizer; this is mainly because it has an incomplete octet of electron configuration in which it lacks one electron to fill up the outermost p orbital. However, it is the weakest oxidizing agent among other halogens due to its large atomic size.

What is Iodide?

Iodide is an anion of iodine. This anion forms when iodine atom obtains an electron from outside. Accordingly, the chemical symbol of iodide is I^– , and the molar mass of this ion is 126.9 g/mol. We name the chemical compounds consisting of this anion commonly as “iodides”. Above all, iodide is the largest monatomic anion because it forms from the iodine atom that has comparatively a large atomic size. Moreover, iodide forms comparatively weak bonds with opposite ions due to the same reason of being a large ion. Also, due to the same reason, iodide is less hydrophilic than other small anions.

Most of the times, compounds containing iodide ions such as iodide salt are water soluble but less than that of chlorides and bromides. In addition to that, the aqueous solutions containing this anion can increase the solubility of iodine molecules (I₂) better than that of pure water.

What is the Difference Between Iodine and Iodide?

Iodine and iodide are closely related terms because iodide is derived from iodine. Therefore, most of the times, we use these two terms interchangeably, which is wrong. This is because iodine is different from iodide. The key difference between iodine and iodide is that the iodine is a chemical element whereas the iodide is an anion. Moreover, there are few other differences such as the number of electrons in each chemical species, the reactivity, etc.

The below infographic provides more facts about the difference between iodine and iodide.

Summary – Iodine vs Iodide

The terms iodine and iodide sound similar, but we cannot use them interchangeably because they are two different chemical species. The key difference between iodine and iodide is that the iodine is a chemical element whereas the iodide is an anion.

Reference:

1. “Iodine.” Wikipedia, Wikimedia Foundation, 17 Oct. 2018. Available here  
2. “Iodide.” Wikipedia, Wikimedia Foundation, 9 Sept. 2018. Available here

Image Courtesy:

1.”Iodine-evaporating”Von Jurii (CC BY 3.0) via Commons Wikimedia
2.”Potassium iodide” (Public Domain) via Commons Wikimedia