Bromine vs. Iodine

What's the Difference?

Bromine and iodine are both halogens found in the periodic table, sharing similar chemical properties. However, they differ in several aspects. Firstly, bromine is a reddish-brown liquid at room temperature, while iodine is a shiny purple-black solid. Bromine has a higher boiling point and is more volatile than iodine. Additionally, bromine is more reactive and toxic compared to iodine. On the other hand, iodine is less reactive and less toxic, making it safer for human consumption. Both elements are used in various applications, such as disinfectants, pharmaceuticals, and dyes, but iodine is more commonly used in medicine due to its lower toxicity.


Atomic Number3553
Atomic Mass79.904126.90447
Electron Configuration[Ar] 3d10 4s2 4p5[Kr] 4d10 5s2 5p5
Group17 (Halogens)17 (Halogens)
State at Room TemperatureLiquidSolid
ColorReddish-brownDark violet
Boiling Point58.8°C184.3°C
Melting Point-7.2°C113.7°C
Density3.1028 g/cm³4.933 g/cm³
Ionization Energy1139.9 kJ/mol1008.4 kJ/mol

Further Detail


Bromine and iodine are both halogens, belonging to Group 17 of the periodic table. They share some similarities in terms of their chemical properties, but they also have distinct characteristics that set them apart. In this article, we will explore the attributes of bromine and iodine, including their physical appearance, chemical reactivity, biological significance, and industrial applications.

Physical Appearance

Bromine is a reddish-brown liquid at room temperature, making it the only nonmetallic element that exists in a liquid state under normal conditions. It has a strong, unpleasant odor and is highly volatile. In contrast, iodine is a shiny, dark purple solid that sublimes into a purple vapor when heated. It has a distinctive odor and can stain the skin and other materials with a brownish color.

Chemical Reactivity

Bromine is a highly reactive element, readily forming compounds with other elements. It is a strong oxidizing agent and can react violently with certain organic compounds, making it a useful reagent in various chemical reactions. On the other hand, iodine is less reactive compared to bromine. It can form compounds with other elements, but its reactivity is generally lower. Iodine is commonly used as an indicator in redox reactions due to its ability to change color.

Biological Significance

Bromine and iodine both play important roles in biological systems. Iodine is an essential element for the synthesis of thyroid hormones, which regulate metabolism and growth. A deficiency in iodine can lead to thyroid disorders, such as goiter. On the other hand, bromine is not considered essential for human health, but it can be found in trace amounts in certain tissues. Bromine compounds are also used as disinfectants and flame retardants in various industries.

Industrial Applications

Bromine and iodine find numerous applications in various industries. Bromine compounds, such as methyl bromide and ethylene dibromide, are used as fumigants to control pests in agriculture. They are also employed in the production of flame retardants, dyes, and pharmaceuticals. Additionally, bromine is used in the manufacturing of certain types of plastics and as a catalyst in chemical reactions. Iodine, on the other hand, is widely used in the production of disinfectants, antiseptics, and pharmaceuticals. It is also utilized in the synthesis of organic compounds, such as dyes and iodinated contrast agents for medical imaging.

Comparison of Physical Properties

When comparing the physical properties of bromine and iodine, several differences can be observed. Bromine has a higher boiling point (-7.2°C) compared to iodine (-33.0°C), which is why it exists as a liquid at room temperature. Bromine also has a higher density (3.12 g/cm³) than iodine (4.93 g/cm³). In terms of solubility, bromine is more soluble in organic solvents, such as chloroform and carbon tetrachloride, while iodine is more soluble in water.

Comparison of Chemical Properties

Chemically, bromine and iodine exhibit some similarities but also display distinct behaviors. Both elements can react with metals to form metal halides, but bromine tends to be more reactive in this regard. Bromine is a stronger oxidizing agent compared to iodine, meaning it is more likely to gain electrons in a chemical reaction. Iodine, on the other hand, is a weaker oxidizing agent and is more likely to lose electrons. This difference in reactivity is evident in their reactions with other elements and compounds.


In conclusion, bromine and iodine are two halogens with unique attributes. Bromine is a reddish-brown liquid with high reactivity, while iodine is a dark purple solid with lower reactivity. Both elements have biological significance, with iodine being essential for thyroid hormone synthesis. Industrially, bromine is used in flame retardants and fumigants, while iodine finds applications in disinfectants and pharmaceuticals. Understanding the similarities and differences between bromine and iodine is crucial for various scientific, industrial, and medical applications.

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