Trisulfur

Key takeaways

Trisulfur belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Trisulfur to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Trisulfur from memory before moving on to harder problems.

Reference excerpt

The S3 molecule, known as trisulfur, sulfur trimer, thiozone, or triatomic sulfur, is a cherry-red allotrope of sulfur. It comprises about 10% of vaporised sulfur at 713 K (440 °C; 824 °F) and 1,333 Pa (10.00 mmHg; 0.1933 psi). It has been observed at cryogenic temperatures as a solid. Under ordinary conditions it converts to cyclooctasulfur.

8 S3 → 3 S8

Structure and bonding In terms of structure and bonding S3 and ozone (O3) are similar. Both adopt bent structures and are diamagnetic. Although represented with S=S double bonds, the bonding situation is more complex. The S–S distances are equivalent and are 191.70±0.01 pm, and with an angle at the central atom of 117.36°±0.006°. However, cyclic S3, where the sulfur atoms are arranged in an equilateral triangle with three single bonds (similar to cyclic ozone and cyclopropane), is calculated to be higher in energy than the bent structure experimentally observed. A similar structure has been predicted for ozone, but has not been observed. The name thiozone was invented by Hugo Erdmann in 1908 who hypothesized that S3 comprises a large proportion of liquid sulfur. However its existence was unproven until the experiments of J. Berkowitz in 1964. Using mass spectrometry, he showed that sulfur vapour contains the S3 molecule. Above 1,200 °C (2,190 °F) S3 is the second most common molecule after S2 in gaseous sulfur. In liquid sulfur the molecule is not common until the temperature is high, such as 500 °C (932 °F). However, small molecules like this contribute to most of the reactivity of liquid sulfur. S3 has an absorption peak of 425 nm (violet) with a tail extending into blue light. S3 can also be generated by photolysis of S3Cl2 embedded in a glass or matrix of solid noble gas.

Natural occurrence S3 occurs naturally on Io in volcanic emissions. S3 is also likely to appear in the atmosphere of Venus at heights of 20 to 30 km, where it is in thermal equilibrium with S2 and S4. The reddish colour of Venus' atmosphere at lower levels is likely to be due to S3.

Reactions S3 reacts with carbon monoxide to make carbonyl sulfide and S2. Formation of compounds with a defined number of sulfur atoms is possible:

S3 + S2O → S5O (cyclic)

Radical anion

Although S3 is elusive under ordinary conditions, the intensely blue radical anion S−3 is abundant. The anion is sometimes called thiozonide, by analogy with the ozonide anion, O−3, to which it is valence isoelectronic. The preferred IUPAC name is trisulfanidylo. The gemstone lapis lazuli and the mineral lazurite (from which the pigment ultramarine is derived) contain S−3. International Klein Blue, developed by Yves Klein, also contains the S−3 radical anion. The blue colour is due to the C2A2 transition to the X2B1 electronic state in the ion, causing a strong absorption band at 610–620 nm or 2.07 eV (in the orange region of the visible spectrum). The Raman frequency is 523 cm−1 and another infrared absorption is at 580 cm−1. The S−3 ion has been shown to be stable in aqueous solution under a pressure of 0.5 GPa (73,000 psi), and is expected to occur naturally at depth in the Earth's crust where subduction or high pressure metamorphism occurs. This ion is probably important in movement of copper and gold in hydrothermal fluids. Lithium hexasulfide (which contains S−6, another polysulfide radical anion) with tetramethylenediamine solvation dissociates acetone and related donor solvents to S−3. The S−3 radical anion was also made by reducing gaseous sulfur with Zn2+ in a matrix. The material is strongly blue-coloured when dry and changes colour to green and yellow in the presence of trace amounts of water. Another way to make it is with polysulfide dissolved in hexamethylphosphoramide where it gives a blue colour. Other methods of production of S−3 include reacting sulfur with partially hydroxylated magnesium oxide at 400 °C. Raman spectroscopy can be used to identify S−3, and it can be used non-destructively in paintings. The bands are 549 cm−1 for symmetric stretch, 585 cm−1 for asymmetric stretch, and 259 cm−1 for bending. Natural materials can also contain S−2 which has an optical absorption at 390 nm and Raman band at 590 cm−1.

Trisulfide ion The trisulfide ion, S2−3 is part of the polysulfide series. The sulfur chain is bent at an angle of 107.88°. Strontium trisulfide (SrS3) has a S–S bond length of 205 pm. The bonds are single. It is isoelectronic to sulfur dichloride.

References

External links Media related to Trisulfur at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Trisulfur

Start with the simplest possible case. Write down what Trisulfur claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Trisulfur before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Trisulfur ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Trisulfur

In research: Trisulfur appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Trisulfur in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Trisulfur is common in secondary-school and first-year university syllabi. It links to neighbouring topics Allotropes of sulfur, Gases with color, Homonuclear triatomic molecules, so understanding it makes those chapters shorter.
In everyday life: Look for Trisulfur outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Trisulfur in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Trisulfur means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Trisulfur out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Trisulfur in simple terms?

The S3 molecule, known as trisulfur, sulfur trimer, thiozone, or triatomic sulfur, is a cherry-red allotrope of sulfur. It comprises about 10% of vaporised sulfur at 713 K (440 °C; 824 °F) and 1,333 Pa (10.00 mmHg; 0.1933 psi).

Why does Trisulfur matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Trisulfur?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Trisulfur.