How does sulfur’s molecular structure change when it is heated?

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A labeled diagram highlights sulfur's position on the periodic table, showing its atomic number 16, symbol S, atomic weight range, electron configuration, and classification as a solid, strongly acidic, orthorhombic nonmetal at room temperature. — sulfur Chemical properties of sulfur.

When sulfur is heated, its molecular structure undergoes significant transformations that alter its physical properties, such as viscosity and color.1

At temperatures just above its melting point (118.9 °C), sulfur exists as a mobile, yellow liquid composed of eight-membered rings. As the temperature rises above 157 °C, these rings rupture, creating reactive units that link together to form long, high-molecular-weight chains. This polymerization causes the liquid's viscosity to increase dramatically, reaching a maximum at approximately 187 °C.1

As heating continues toward the boiling point (444.6 °C), these long chains eventually break down into smaller fragments. Upon vaporization, the sulfur reverts to cyclic molecules like $S_{8}$ and $S_{6}$ . At even higher temperatures, the structure continues to simplify: $S_{2}$ becomes the predominant form at about 900 °C, and the element dissociates into monatomic sulfur above 1,800 °C.1