List of Allotropes and Forms
Allotropes are in bold.
| Formula/name | Common name | Other names | Notes |
|---|---|---|---|
| S2 | disulfur | A diatomic gas with a triplet ground state like dioxygen. | |
| S3 | trisulfur | A cherry red triatomic gas with a bent ozone-like structure. | |
| S4 | tetrasulfur | Structure not determined but calculations indicate it to be cyclo-S4. | |
| cyclo-S5 | cyclo-pentasulfur | Not yet isolated, only detected in sulfur vapour. | |
| cyclo-S6 | ρ-sulfur | cyclo-hexasulfur, "ε-sulfur", "Engel's" sulfur, "Aten's sulfur" | The ring adopts a chair form in the solid. |
| cyclo-S6/cyclo-S10 adduct | A mixed crystal with alternating layers of cyclo-S6 and cyclo-S10. | ||
| cyclo-S7 | α-, β-, γ-, δ- cycloheptasulfur | Four forms known, two(γ-, δ- ) characterized. | |
| cyclo-S8 | α-sulfur | "orthorhombic sulfur" "rhombic sulfur", "flowers of sulfur", "roll sulfur" "milk of sulfur", "Muthmann's sulfur I" | Yellow solid consisting of S8 puckered rings. The thermodynamically stable form at ordinary temperatures. |
| cyclo-S8 | β-sulfur | "monoclinic sulfur" "prismatic sulfur" "Muthmann's sulfur II" | Yellow crystalline solid, consisting of S8 puckered rings. Only stable above 95.6 °C, it reverts to α-sulfur at room temperature. |
| cyclo-S8 | γ-sulfur | "nacreous sulfur" "mother of pearl sulfur" "Gernez’s sulfur" or "Muthmann's sulfur III". | Light yellow solid, crystal monoclinic, consisting of S8 puckered rings. Found in nature as the rare mineral rosickyite. |
| cyclo-Sn n = 9–15, 18, 20 |
cyclo-(nona; deca; undeca; dodeca; trideca; tetradeca; pentadeca; octadeca; eicosa)sulfur | Pure forms all allotropes, cyclo-S9 has four forms, cyclo-S18 has two forms. Generally synthesised rather than obtained by treatment of another form of elemental sulfur. | |
| catena-Sx | fibrous (ψ) sulfur | Well characterized, contains parallel helical sulfur chains and is difficult to obtain pure. | |
| catena-Sx | lamina sulfur | Not well characterized, contains helical chains partially crossed. | |
| amorphous sulfur | Quenched molten sulfur plastic sulfur at first crystallises to amorphous or glassy sulfur. Consists of a mixture of catena sulfur and cyclo sulfur. | ||
| insoluble sulfur | Quenched liquid sulfur with soluble species extracted with CS2. Sometimes called polymeric sulfur, μ-S or ω-S. | ||
| φ-sulfur | A mixture of allotropic ψ-sulfur and cyclo forms mainly γ-cyclo-S8. | ||
| ω-sulfur | insoluble sulfur | A mixture of chains with a minimum of soluble species. | |
| λ-sulfur | Light yellow mobile liquid formed when β-sulfur first melts at 119.6 °C. Consists of S8 rings. | ||
| μ-sulfur | The dark-coloured viscous liquid formed when π-sulfur is heated and the solid when cooled. Contains a mixture of polymeric chains. | ||
| π-sulfur | Dark-coloured liquid that develops as λ-sulfur is left molten. Contains mixture of Sn rings. | ||
| High-pressure forms of α-sulfur | S-II, S-III, S-IV, S-V and others | Four high-pressure phases (at ambient temperature) including two that are metallic and become superconducting at low temperature and some additional phases photo-induced below 20–30 GPa. | |
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