physics

Magnesium fluoride

Magnesium fluoride is a physics 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 Magnesium fluoride rather than just read about it. In short: Magnesium fluoride is an ionically bonded inorganic compound with the formula MgF2. The compound is a colorless to white crystalline salt that is transparent over a wide range of wavelengths, such that it is used in the optical windows of space telescopes.

Key takeaways

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

Reference excerpt

Magnesium fluoride is an ionically bonded inorganic compound with the formula MgF2. The compound is a colorless to white crystalline salt that is transparent over a wide range of wavelengths, such that it is used in the optical windows of space telescopes. It occurs naturally as the rare mineral sellaite.

Production Magnesium fluoride is prepared from magnesium oxide with sources of hydrogen fluoride such as ammonium bifluoride, by the breakdown of it:

MgO + [NH4]HF2 → MgF2 + NH3 + H2O Related metathesis reactions are also feasible:

Mg(OH)2 + CuF2 → MgF2 + Cu(OH)2

Structure The compound crystallizes as tetragonal birefringent crystals. The structure of the magnesium fluoride is similar to that of rutile, featuring octahedral Mg2+ cations and 3-coordinate F− anions.

In the gas phase, monomeric MgF2 molecules adopt a linear molecular geometry.

Uses

Optics Magnesium fluoride is transparent over an extremely wide range of wavelengths. Windows, lenses, and prisms made of this material can be used over the entire range of wavelengths from 0.120 μm (vacuum ultraviolet) to 8.0 μm (infrared). High-quality, synthetic magnesium fluoride is one of two materials (the other being lithium fluoride) that will transmit in the vacuum ultraviolet range at 121 nm (Lyman alpha). Magnesium fluoride is tough and polishes well but is slightly birefringent and should therefore be cut with the optic axis perpendicular to the plane of the window or lens. Due to its suitable refractive index of 1.37, magnesium fluoride is commonly applied in thin layers to the surfaces of optical elements as an inexpensive anti-reflective coating. Its Verdet constant is 0.00810 arcmin⋅G−1⋅cm−1 at 632.8 nm.

Safety Chronic exposure to magnesium fluoride may affect the skeleton, kidneys, central nervous system, respiratory system, eyes and skin, and may cause or aggravate attacks of asthma.

References

External links Infrared windows at Lawrence Berkeley National Laboratory National Pollutant Inventory - Fluoride and compounds fact sheet Crystran Data Archived 2012-03-21 at the Wayback Machine Crystran MSDS

Illustrations

Worked examples

Example 1 — a first encounter with Magnesium fluoride

Start with the simplest possible case. Write down what Magnesium fluoride 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 Magnesium fluoride 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 Magnesium fluoride 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 Magnesium fluoride

In research: Magnesium fluoride 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 Magnesium fluoride 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: Magnesium fluoride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alkaline earth metal halides, Fluorides, Magnesium compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Magnesium fluoride 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 Magnesium fluoride in 20 minutes

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

Frequently asked questions

What is Magnesium fluoride in simple terms?

Why does Magnesium fluoride 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 Magnesium fluoride?

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 Magnesium fluoride.