Samarium

Key takeaways

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

Reference excerpt

Samarium is a chemical element; it has symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samarium(II) are also known, most notably the monoxide SmO, monochalcogenides SmS, SmSe and SmTe, as well as samarium(II) iodide. Discovered in 1879 by French chemist Paul-Émile Lecoq de Boisbaudran, samarium was named after the mineral samarskite from which it was isolated. The mineral was named after a Russian mine official, Vassili Samarsky-Bykhovets, who thus became the first person to have a chemical element named after him, though the name was indirect. Samarium occurs in concentration up to 2.8% in several minerals including cerite, gadolinite, samarskite, monazite and bastnäsite, the last two being the most common commercial sources of the element. These minerals are mostly found in China, the United States, Brazil, India, Sri Lanka and Australia; China is by far the world leader in samarium mining and production. The main commercial use of samarium is in samarium–cobalt magnets, which have permanent magnetization second only to neodymium magnets; however, samarium compounds can withstand significantly higher temperatures, above 700 °C (1,292 °F), without losing their permanent magnetic properties. The radioisotope samarium-153 is the active component of the drug samarium (153Sm) lexidronam (Quadramet), which kills cancer cells in lung cancer, prostate cancer, breast cancer and osteosarcoma. Another isotope, samarium-149, is a strong neutron absorber and so is added to control rods of nuclear reactors. It also forms as a decay product during reactor operation and is one of the important factors considered in reactor design and operation. Other uses of samarium include catalysis of chemical reactions, radioactive dating and X-ray lasers. Samarium(II) iodide, in particular, is a common reducing agent in chemical synthesis. Samarium has no biological role; some samarium salts are slightly toxic.

Physical properties Samarium is a rare earth element with a hardness and density similar to zinc. With a boiling point of 1,794 °C (3,261 °F), samarium is the third most volatile lanthanide after ytterbium and europium and comparable in this respect to lead and barium; this helps separation of samarium from its ores. When freshly prepared, samarium has a silvery lustre, and takes on a duller appearance when oxidized in air. Samarium is calculated to have one of the largest atomic radii of the elements; with a radius of 238 pm, only potassium, praseodymium, barium, rubidium and caesium are larger. In ambient conditions, samarium has a rhombohedral structure (α form). Upon heating to 731 °C (1,348 °F), its crystal symmetry changes to hexagonal close-packed (hcp), though its actual transition temperature depends on the metal purity. Further heating to 922 °C (1,692 °F) transforms the metal into a body-centered cubic (bcc) phase. Heating to 300 °C (572 °F) plus compression to 40 kbar results in a double-hexagonally close-packed structure (dhcp). Higher pressure of the order of hundreds or thousands of kilobars induces a series of phase transformations, in particular with a tetragonal phase appearing at about 900 kbar. In one study, the dhcp phase could be produced without compression, using a nonequilibrium annealing regime with a rapid temperature change between about 400 °C (752 °F) and 700 °C (1,292 °F), confirming the transient character of this samarium phase. Thin films of samarium obtained by vapor deposition may contain the hcp or dhcp phases in ambient conditions. Samarium and its sesquioxide are paramagnetic at room temperature. Their corresponding effective magnetic moments, below 2 bohr magnetons, are the third-lowest among lanthanides (and their oxides) after lanthanum and lutetium. The metal transforms to an antiferromagnetic state upon cooling to 14.8 K. Individual samarium atoms can be isolated by encapsulating them into fullerene molecules. They can also be intercalated into the interstices of the bulk C60 to form a solid solution of nominal composition Sm3C60, which is superconductive at a temperature of 8 K. Samarium doping of iron-based superconductors – a class of high-temperature superconductor – increases their transition to normal conductivity temperature up to 56 K, the highest value achieved so far in this series.

Chemical properties In air, samarium slowly oxidizes at room temperature and spontaneously ignites at 150 °C (302 °F). Even when stored under mineral oil, samarium gradually oxidizes and develops a grayish-yellow powder of the oxide-hydroxide mixture at the surface. The metallic appearance of a sample can be preserved by sealing it under an inert gas such as argon. Samarium is quite electropositive and reacts slowly with cold water and rapidly with hot water to form samarium hydroxide:

2Sm(s) + 6H2O(l) → 2Sm(OH)3(aq) + 3H2(g) Samarium dissolves readily in dilute sulfuric acid to form solutions containing the yellow to pale green Sm(III) ions, which exist as [Sm(OH2)9]3+ complexes:

2Sm(s) + 3H2SO4(aq) → 2Sm3+(aq) + 3SO2−4(aq) + 3H2(g) Samarium is one of the few lanthanides with a relatively accessible +2 oxidation state, alongside Eu and Yb. Sm2+ ions are blood-red in aqueous solution.

Compounds

Oxides The most stable oxide of samarium is the sesquioxide Sm2O3. Like many samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt. The melting point of Sm2O3 is high (2345 °C), so it is usually melted not by direct heating, but with induction heating, through a radio-frequency coil. Sm2O3 crystals of monoclinic symmetry can be grown by the flame fusion method (Verneuil process) from Sm2O3 powder, that yields cylindrical boules up to several centimeters long and about one centimeter in diameter. The boules are transparent when pure and defect-free and are orange otherwise. Heating the metastable trigonal Sm2O3 to 1,900 °C (3,450 °F) converts it to the more stable monoclinic phase. Cubic Sm2O3 has also been described. Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm2O3 with samarium metal at high temperature (1000 °C) and a pressure above 50 kbar; lowering the pressure resulted in incomplete reaction. SmO has cubic rock-salt lattice structure.

Chalcogenides

… excerpt ends here. Continue reading the full article.

Illustrations

Samarium: Samarium trichloride — Samarium trichloride

Worked examples

Example 1 — a first encounter with Samarium

Start with the simplest possible case. Write down what Samarium 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 Samarium 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 Samarium 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 Samarium

In research: Samarium 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 Samarium 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: Samarium is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chemical elements, Chemical elements with rhombohedral structure, Lanthanides, so understanding it makes those chapters shorter.
In everyday life: Look for Samarium 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 Samarium in 20 minutes

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

Frequently asked questions

What is Samarium in simple terms?

Samarium is a chemical element; it has symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air.

Why does Samarium 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 Samarium?

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 Samarium.