chemistry

Plutonium sulfides

Plutonium sulfides is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Plutonium sulfides rather than just read about it. In short: Plutonium sulfides are compounds of plutonium and sulfur, where sulfur exists as sulfide or polysulfide ions and plutonium exists in the trivalent state or tetravalent state. They have a general formula PuxSy.

Key takeaways

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

Reference excerpt

Plutonium sulfides are compounds of plutonium and sulfur, where sulfur exists as sulfide or polysulfide ions and plutonium exists in the trivalent state or tetravalent state. They have a general formula PuxSy. Known plutonium sulfides include PuS, Pu3S4, Pu5S7, Pu2S3, and PuS2. Plutonium oxysulfides (mixed oxide-sulfides) are also known, including Pu2O2S, Pu4O4S3, PuOS, and Pu2O2S3. Many of them are isostructural to the corresponding neptunium sulfides.

Plutonium monosulfide

Plutonium monosulfide is a yellow solid with the formula PuS. Unlike neptunium and uranium monosulfide, it contains plutonium in its tetravalent state, rather than trivalent. It is produced in several chemical reactions: It is formed during the reaction of plutonium metal and sulfur gas:

Pu + S → PuS It is also formed when plutonium sesquisulfide is reduced by plutonium hydride. Reacting ground plutonium metal with hydrogen sulfide also produces plutonium monosulfide. It is nonmagnetic, and is a semiconductor with a high electrical resistivity and a small energy gap. It is a non-stoichiometric compound, having a range between around PuS0.95 and PuS1.00. At Pu:S ratios lower than 0.95 or higher than 1.00, it exists in equilibrium with plutonium metal or plutonium sesquisulfide, respectively. At room temperature and pressure, it adopts the rock salt structure. Its structure is cubic, with space group Fm3m and lattice parameter a=5.23–5.24 Å depending on stoichiometry; its lattice parameter decreases with decreasing sulfur content. It does not exhibit a phase transition up to 60 GPa, but theoretical predictions it should undergo a phase transition to a caesium chloride-type structure at 105 GPa, undergoing a 3.6% volume loss.

Plutonium sesquisulfide

Plutonium sesquisulfide has the formula Pu2S3. It can be formed from the reaction between plutonium metal and sulfur gas:

2 Pu + 3 S → Pu2S3 Or from the thermal decomposition of plutonium disulfide:

2 PuS2 → Pu2S3 + S Three polymorphs of plutonium sesquisulfide are known: α-Pu2S3, β-Pu2S3 and γ-Pu2S3, though β-Pu2S3 is a ternary oxysulfide and can feature incorporated oxygen. Like with the neptunium sulfides, α-Pu2S3 is a stoichiometric compound, while β-Pu2S3 and γ-Pu2S3 have variable composition. β-Pu2S3 is a solid solution between Pu10S14O and Pu2S3 (formula Pu10S15-xOx) and γ-Pu2S3 is substoichiometric with an ideal composition of Pu3S4. α-Pu2S3 is the dominant form of Pu2S3 up to 1100 °C. At 1100 °C, it decomposes to the β-Pu2S3, and at 1550 °C, β-Pu2S3 decomposes to γ-Pu2S3. γ-Pu2S3 melts above 1700 °C; however, its melting point is dependent on its stoichiometry. Pu2S3 melts around 1725 °C, but Pu3S4 melts around 1820 °C.

Structural properties α-Pu2S3 has the same structure as the related rare earth compounds, having the La2S3-type structure, isostructural with α-Np2S3 and α-Ce2S3. It features a framework of PuS7 and PuS8 polyhedra. Its crystals are orthorhombic, with lattice parameters a=3.97, b=7.37, and c=15.45 Å. It has a density of 8.31 g/cm3 and space group Pnma. While early reports suggested β-Pu2S3 was a binary substoichiometric sulfide, it was later shown that the rare earth sesquisulfide phases, including β-Pu2S3, actually contain variable amounts of oxygen as opposed to sulfur vacancies, and it is now known to have variable composition between Pu2S3 and Pu10S14O, with a single site where oxygen and sulfur substitute for each other. It adopts a complex tetragonal structure of space group I41/acd which notably contains a Pu4O tetrahedron. One crystal of this compound was found to have lattice parameters a=14.90, b=19.78 Å. γ-Pu2S3 adopts a Th3P4-type structure of space group I43d and bcc symmetry, where each plutonium atoms is coordinated to 8 atoms of sulfur. It extends over a large range of stoichiometries, from Pu3S4 to Pu2S3. Its lattice parameter is dependent on its stoichiometry; Pu3S4 has lattice parameter around a=8.415 Å, while Pu2S3 has lattice parameter a=8.453–8.459 Å, though this depends on the exact conditions.

Plutonium disulfide Plutonium disulfide has the formula PuS2. It is the highest sulfide of plutonium. It is formed by the reaction of plutonium hydride and sulfur in a sealed tube for one week at about 350 °C to 750 °C, or by reacting plutonium and sulfur vapor together:

Pu + 2S → PuS2 It adopts an anti-Fe2As type structure, with distortions that arise from disulfide bonding between sulfur atoms. It is often substoichiometric, and its composition range extends from PuS2.0 to around PuS1.76. Its structure can be either tetragonal (space group P4/nmm) or monoclinic (space group P21/a), though the monoclinic phase can only be found at the exact composition PuS2. Its lattice parameters vary depending on sulfur content; PuS1.76 has lattice parameters a=3.936 and c=7.958 Å, PuS1.9 has lattice parameters a=3.943 and c=7.962 Å, and tetragonal PuS2.0 has lattice parameters a=3.974 and c=7.947 Å. The monoclinic PuS2.0 phase has lattice parameters a=7.962, b=3.981, c=7.962 Å, and β=90°. Plutonium disulfide is thermally unstable, and upon calcination, it decomposes to lower plutonium sulfides. PuS2 first loses sulfur at 500 °C to give PuS1.9, which further loses sulfur at 580 °C to give α-Pu2S3.

See also Neptunium sulfides Plutonium oxysulfides

References

Illustrations

Worked examples

Example 1 — a first encounter with Plutonium sulfides

Start with the simplest possible case. Write down what Plutonium sulfides claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Plutonium sulfides 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 Plutonium sulfides 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 Plutonium sulfides

In research: Plutonium sulfides appears in chemistry 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 Plutonium sulfides 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: Plutonium sulfides is common in secondary-school and first-year university syllabi. It links to neighbouring topics Plutonium compounds, Sulfides, so understanding it makes those chapters shorter.
In everyday life: Look for Plutonium sulfides 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.

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How to study Plutonium sulfides in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Plutonium sulfides 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 Plutonium sulfides out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Plutonium sulfides in simple terms?

Why does Plutonium sulfides matter?

Because it connects several chemistry 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 Plutonium sulfides?

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 Plutonium sulfides.