What is the Difference Between Rhombic and Monoclinic Sulphur

Rhombic and monoclinic sulphur are two allotropes of the element sulphur. Each has its own molecular arrangement and properties. In this article, we’ll explore the difference between rhombic and monoclinic sulphur, and their relevance in scientific and industrial applications.

What is the difference between rhombic and monoclinic sulphur? Rhombic sulphur has a stable crystalline form with a rhombic or octahedral shape, while monoclinic sulphur has a different crystal structure with monoclinic symmetry.

Key Areas Covered

1. What is Rhombic Sulphur  
      – Definition, Features 
2. What is Monoclinic Sulphur
      – Definition, Features 
3. Similarities Between Rhombic and Monoclinic Sulphur
      – Outline of Common Features
4. Difference Between Rhombic and Monoclinic Sulphur
      – Comparison of Key Differences
5. FAQ: Rhombic and Monoclinic Sulphur
      – Answers to Frequently Asked Questions

Key Terms

Rhombic Sulphur, Monoclinic Sulphur

Difference Between Rhombic and Monoclinic Sulphur - Comparison Summary

What is Rhombic Sulphur

Rhombic sulphur is one of the allotropes of elemental sulphur, existing in a crystalline form with a distinctive rhombic structure. In this allotrope, sulphur atoms form puckered rings that arrange themselves in a layered, crystalline lattice. These rhombic crystals are stable at temperatures below 95.6°C, above which they undergo a reversible transformation into monoclinic sulphur.

The rhombic form of sulphur is important in various fields, particularly in chemistry and materials science. Its stability and well-defined structure make it a valuable subject for research and experimentation. Scientists have extensively studied the phase transitions between rhombic and monoclinic sulphur, unraveling the intricate dynamics of sulphur’s polymorphic behavior.

Rhombic and Monoclinic Sulphur

Interestingly, rhombic sulphur is often used in crystallography studies as a model system due to its relatively simple structure. Understanding the properties and transitions of rhombic sulphur aids in broader comprehension of sulphur’s behavior across different forms and conditions.

Moreover, the allotropy of sulphur plays a role in industrial applications, such as vulcanization in rubber manufacturing and the production of sulphuric acid. The ability to control and manipulate sulphur’s allotropes is crucial for optimizing these processes.

What is Monoclinic Sulphur

In its monoclinic crystalline structure, sulphur atoms arrange themselves in a lattice with unique geometric characteristics. Unlike rhombic sulphur, monoclinic sulphur has a distinct crystallographic symmetry, specifically a monoclinic crystal system characterized by unequal axis lengths and a non-right angle between two of the crystal axes.

Monoclinic sulphur exhibits a distinctive prismatic crystal shape with oblique angles, giving it a unique appearance under microscopic examination. This form of sulphur is stable at higher temperatures, and its transition from rhombic to monoclinic often occurs as it undergoes phase changes.

Monoclinic Sulphur

The properties of monoclinic sulphur play a crucial role in understanding sulphur’s behavior in different conditions, particularly in the context of sulphur allotropes. Its stability and structural features contribute to the study of sulphur’s role in various chemical and physical processes, including its involvement in the formation of crystals, polymers, and sulphur allotrope transformations. Researchers explore these properties to gain insights into the broader applications of sulphur in fields such as materials science, chemistry, and geology.

Similarities Between Rhombic and Monoclinic Sulphur

  1. Rhombic and monoclinic sulphur are two of the several allotropes of sulphur.
  2. Both rhombic and monoclinic sulphur consist of S8 molecules, where eight sulphur atoms are arranged in a crown-like structure.

Difference Between Rhombic and Monoclinic Sulphur


  • Rhombic sulphur is a crystal structure in which sulphur atoms form puckered rings, giving it a rhombic appearance, while monoclinic sulphur is a crystal structure where sulphur atoms form chains, resulting in a monoclinic lattice arrangement.


  • While rhombic sulphur is stable at room temperature and normal pressure conditions, monoclinic sulphur is stable at higher temperatures and under certain pressure conditions.

Chemical Reactivity

  • Rhombic sulphur is less reactive compared to monoclinic sulphur, while monoclinic sulphur shows greater reactivity, especially at higher temperatures.


  • Furthermore, rhombic sulphur is commonly used in the vulcanization of rubber, production of sulphuric acid, and certain pharmaceutical applications, whereas monoclinic sulphur finds applications in chemical synthesis, especially in organic chemistry reactions where its higher reactivity is advantageous.


In conclusion, rhombic and monoclinic are distinct allotropes of elemental sulphur, each with its unique crystal structure and stability conditions. Rhombic sulphur, characterized by a rhombic crystal lattice, remains stable at room temperature, while monoclinic sulphur exhibits a monoclinic crystal structure and stability at higher temperatures. Both allotropes share the S8 molecule arrangement in crown-like structures. The study of the difference between rhombic and monoclinic sulphur contributes to a deeper understanding of sulphur’s behavior, impacting diverse fields.

FAQ: Rhombic and Monoclinic Sulphur

1. Is monoclinic sulphur soluble in water?

Both rhombic and monoclinic sulphur exhibit solubility in carbon disulfide but are insoluble in water due to their non-polar nature. This characteristic makes them useful in certain organic reactions where non-aqueous solvents are preferred.

2. What is the structure of rhombic sulphur?

The structure of rhombic sulphur consists of S8 molecules, where eight sulphur atoms are arranged in a puckered ring formation. Each sulphur atom in the ring is bonded to two adjacent sulphur atoms, forming covalent S-S bonds. The distance between sulphur atoms within the ring is approximately 2.12 angstroms (2.12 Å), reflecting the bond length of the S-S bond in the molecule.

3. Is monoclinic sulphur colourless?

Yes, monoclinic sulphur is colorless. When rhombic sulphur is melted and subsequently cooled, it transforms into monoclinic sulphur, resulting in the formation of colorless needle-shaped crystals.

4. What is the difference between monoclinic and orthorhombic?

The main difference between monoclinic and orthorhombic crystal systems lies in their respective angles between the crystallographic axes. In monoclinic crystals, one axis has a different length and intersects the other two at oblique angles, while in orthorhombic crystals, all three axes are of different lengths and intersect each other at right angles.

5. Why density of rhombic sulphur is higher than monoclinic sulphur?

Rhombic sulphur is denser than monoclinic sulphur. This difference in density is due to the different arrangements of sulphur atoms in their crystal structures. Rhombic sulphur has a denser packing arrangement of atoms compared to monoclinic sulphur, resulting in a higher overall density.


1. “Monoclinic sulphur.” Simply Science.
2. “Chemistry of sulphur (Z=16).” LibreText. Chemistry.

Image Courtesy:

1. “PSM V83 D031 Crystals of needle like or monoclinic sulphur” By Unknown author – Popular Science Monthly Volume 83 (Public Domain) via Commons Wikimedia
2. “sulphur – El Desierto mine, San Pablo de Napa, Daniel Campos Province, Potosí, Bolivia” By Ivar Leidus – Own work (CC BY-SA 4.0) via Commons Wikimedia

About the Author: Hasini A

Hasini is a graduate of Applied Science with a strong background in forestry, environmental science, chemistry, and management science. She is an amateur photographer with a keen interest in exploring the wonders of nature and science.

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