chemistry

Holmium

Holmium 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 Holmium rather than just read about it. In short: Holmium is a chemical element; it has symbol Ho and atomic number 67. It is a rare-earth element and the eleventh member of the lanthanide series of elements.

Key takeaways

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

Reference excerpt

Holmium is a chemical element; it has symbol Ho and atomic number 67. It is a rare-earth element and the eleventh member of the lanthanide series of elements. It is a relatively soft, silvery, fairly corrosion-resistant and malleable metal. Like many other lanthanides, holmium is too reactive to be found in native form, as pure holmium slowly forms a yellowish oxide coating when exposed to air. When isolated, holmium is relatively stable in dry air at room temperature. However, it reacts with water and corrodes readily, and also burns in air when heated. In nature, holmium occurs together with the other rare-earth metals (like thulium). It is a relatively rare lanthanide, making up 1.4 parts per million of the Earth's crust, an abundance similar to tungsten. Holmium was discovered through isolation by Swedish chemist Per Theodor Cleve. It was also independently discovered by Jacques-Louis Soret and Marc Delafontaine, who together observed it spectroscopically in 1878. Its oxide was first isolated from rare-earth ores by Cleve in 1878. The element's name comes from Holmia, the Latin name for the city of Stockholm. Like many other lanthanides, holmium is found in the minerals monazite and gadolinite and is usually commercially extracted from monazite using ion-exchange techniques. Its compounds in nature and in nearly all of its laboratory chemistry are trivalently oxidized, containing Ho(III) ions. Trivalent holmium ions have fluorescent properties similar to many other rare-earth ions (while yielding their own set of unique emission light lines), and thus are used in the same way as some other rare earths in certain laser and glass-colorant applications. Holmium has the highest magnetic permeability and magnetic saturation of any element and is thus used for the pole pieces of the strongest static magnets. Because holmium strongly absorbs neutrons, it is also used as a burnable poison in nuclear reactors.

Properties Holmium is the eleventh member of the lanthanide series. In the periodic table, it appears in period 6, between the lanthanides dysprosium to its left and erbium to its right, and above the actinide einsteinium.

Physical properties With a boiling point of 3,000 K (2,727 °C; 4,940 °F), holmium is the sixth most volatile lanthanide after ytterbium, europium, samarium, thulium and dysprosium. At standard temperature and pressure, holmium, like many of the second half of the lanthanides, normally assumes a hexagonally close-packed (hcp) structure. Its 67 electrons are arranged in the configuration [Xe] 4f11 6s2, so that it has thirteen valence electrons filling the 4f and 6s subshells. Holmium, like all of the lanthanides, is paramagnetic at standard temperature and pressure. However, holmium is ferromagnetic at temperatures below 19 K (−254.2 °C; −425.5 °F). It has the highest magnetic moment (10.6 μB) of any naturally occurring element and possesses other unusual magnetic properties. When combined with yttrium, it forms highly magnetic compounds.

Chemical properties Holmium metal tarnishes slowly in air, forming a yellowish oxide layer that has an appearance similar to that of iron rust. It burns readily to form holmium(III) oxide:

4 Ho + 3 O2 → 2 Ho2O3 It is a relatively soft and malleable element that is fairly corrosion-resistant and chemically stable in dry air at standard temperature and pressure. In moist air and at higher temperatures, however, it quickly oxidizes, forming a yellowish oxide. In pure form, holmium possesses a metallic, bright silvery luster. Holmium is quite electropositive: on the Pauling electronegativity scale, it has an electronegativity of 1.23. It is generally trivalent. It reacts slowly with cold water and quickly with hot water to form holmium(III) hydroxide:

2 Ho (s) + 6 H2O (l) → 2 Ho(OH)3 (aq) + 3 H2 (g) Holmium metal reacts with all the stable halogens:

2 Ho (s) + 3 F2 (g) → 2 HoF3 (s) [pink] 2 Ho (s) + 3 Cl2 (g) → 2 HoCl3 (s) [yellow] 2 Ho (s) + 3 Br2 (g) → 2 HoBr3 (s) [yellow] 2 Ho (s) + 3 I2 (g) → 2 HoI3 (s) [yellow] Holmium dissolves readily in dilute sulfuric acid to form solutions containing the yellow Ho(III) ions, which exist as a [Ho(OH2)9]3+ complexes:

2 Ho (s) + 3 H2SO4 (aq) → 2 Ho3+ (aq) + 3 SO2−4 (aq) + 3 H2 (g)

Oxidation states As with many lanthanides, holmium is usually found in the +3 oxidation state, forming compounds such as holmium(III) fluoride (HoF3) and holmium(III) chloride (HoCl3). Holmium in solution is in the form of Ho3+ surrounded by nine molecules of water. Holmium dissolves in acids. However, holmium is also found to exist in +2, +1 and 0 oxidation states.

Isotopes

Natural holmium consists of one primordial isotope, holmium-165. It is observationally stable, though theoretically should undergo alpha decay to terbium-161 with a very long half-life. The known isotopes of holmium range from 140Ho to 175Ho. The primary decay mode before the stable 165Ho, is beta plus decay to dysprosium isotopes, and the primary mode after is beta minus decay to erbium isotopes. Of the 35 synthetic radioactive isotopes among these, the most stable one is holmium-163 (163Ho), with a half-life of 4570 years. The next most stable is holmium-166 (166Ho) having a half-life of 26.812 hours, and others have half-lives under 4 hours. The metastable isomer 166m1Ho has the unusually long half-life of 1133 years. With a very low excitation energy, it does not decay to the ground state but beta-decays directly, having a particularly rich spectrum of gamma rays, making this isotope useful as a means for calibrating gamma ray spectrometers. Holmium-166 (ground state) has been studied for medical application.

Compounds

Oxides and chalcogenides

… excerpt ends here. Continue reading the full article.

Illustrations

Holmium: A solution of 4% holmium oxide in 10% perchloric acid, permanently fused into a quartz cuvette as an optical calibration standard — A solution of 4% holmium oxide in 10% perchloric acid, permanently fused into a quartz cuvette as an optical calibration standard

Worked examples

Example 1 — a first encounter with Holmium

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

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

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

Frequently asked questions

What is Holmium in simple terms?

Holmium is a chemical element; it has symbol Ho and atomic number 67. It is a rare-earth element and the eleventh member of the lanthanide series of elements.

Why does Holmium 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 Holmium?

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 Holmium.