chemistry

Nitrogen pentafluoride

Nitrogen pentafluoride 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 Nitrogen pentafluoride rather than just read about it. In short: Nitrogen pentafluoride is a theoretical compound of nitrogen and fluorine with the chemical formula NF5. It is hypothesized to exist based on the existence of the pentafluorides of the atoms below nitrogen in the periodic table, such as phosphorus pentafluoride.

Key takeaways

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

Reference excerpt

Nitrogen pentafluoride is a theoretical compound of nitrogen and fluorine with the chemical formula NF5. It is hypothesized to exist based on the existence of the pentafluorides of the atoms below nitrogen in the periodic table, such as phosphorus pentafluoride. Theoretical models of the nitrogen pentafluoride molecule are either a trigonal bipyramidal covalently bound molecule with symmetry group D3h, or [NF4]+F− (tetrafluoroammonium fluoride), which would be an ionic solid.

Ionic solid A variety of other tetrafluoroammonium salts are known ([NF4]+X−), as are fluoride salts of other ammonium cations ([NR4]+F−). In 1966, W. E. Tolberg first synthesized a five-valent nitrogen compound of nitrogen and fluorine when tetrafluoroammonium compounds, tetrafluoroammonium hexafluoroantimonate(V) [NF4]+[SbF6]− and tetrafluoroammonium hexafluoroarsenate(V) [NF4]+[AsF6]− were made. In 1971 C. T. Goetschel announced the preparation of [NF4]+[BF4]− and also produced a white solid assumed to be tetrafluoroammonium fluoride ([NF4]+F−). This was made by treating nitrogen trifluoride and fluorine with 3 MeV electron radiation at 77 K. It decomposed above 143 K back into those ingredients. Theoretical studies also show the ionic compound is very likely to decompose to nitrogen trifluoride and fluorine gas. Karl O. Christe synthesised bis(tetrafluoroammonium) hexafluoronickelate(IV) ([NF4]+)2[NiF6]2−. He also prepared compounds with manganese, a fluorouranate, tetrafluoroammonium perchlorate [NF4]+ClO−4, tetrafluoroammonium fluorosulfate [NF4]+SO3F− and [N2F3]+ (trifluorodiazenium) salts. Christe attempted to make [NF4]+F− by metathesis of [NF4]+[SbF6]− with CsF in HF solvent at 20 °C. However, a variant, tetrafluoroammonium bifluoride hydrofluorates ([NF4]+[HF2]−·nHF), was produced. At room temperature it was a milky liquid, but when cooled, turned pasty. At −45 °C it had the form of a white solid. When reheated it frothed, giving off F2, HF and NF3 as gases. This has CAS number 71485-49-9. I. J. Solomon believed that nitrogen pentafluoride was produced by the thermal decomposition of [NF4]+[AsF6]−, but experimental results were not reproduced. Dominik Kurzydłowski and Patryk Zaleski-Ejgierd predict that a mixture of fluorine and nitrogen trifluoride under pressure between 10 and 33 GPa forms [NF4]+F− with space group R3m. This is a high-pressure oxidation. Over 33 GPa it will form a stable ionic compound with formula ([NF4]+)2[NF6]−F− (bis(tetrafluoroammonium) hexafluoronitrate(V) fluoride) with space group I4/m. Over 151 GPa this is predicted to transform to [NF4]+[NF6]− (tetrafluoroammonium hexafluoronitrate(V)) with space group P4/n. A NF5 molecular compound is not stable under any pressure conditions.

Covalent molecule

For a NF5 molecule to form, five fluorine atoms have to be arranged around a nitrogen atom. There is insufficient space to do this at typical nitrogen–fluorine covalent-bond lengths, so at least some bonds are forced to be longer. Calculations show that fragmentation to form NF4 and F radicals would have a transition state barrier of around 66–84 kJ/mol (15.8–20.0 kcal/mol) and that this process is thermodynamically favourable (exothermic) by 38 kJ/mol (9 kcal/mol). Nitrogen pentafluoride also violates the octet rule in which compounds with eight outer shell electrons are particularly stable.

References

Illustrations

Nitrogen pentafluoride: Possible structure of NF5 (left) and analogous fluorohydrides — Possible structure of NF5 (left) and analogous fluorohydrides

Worked examples

Example 1 — a first encounter with Nitrogen pentafluoride

Start with the simplest possible case. Write down what Nitrogen pentafluoride 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 Nitrogen pentafluoride 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 Nitrogen pentafluoride 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 Nitrogen pentafluoride

In research: Nitrogen pentafluoride 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 Nitrogen pentafluoride 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: Nitrogen pentafluoride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hypothetical chemical compounds, Nitrogen(V) compounds, Nitrogen fluorides, so understanding it makes those chapters shorter.
In everyday life: Look for Nitrogen pentafluoride 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 Nitrogen pentafluoride in 20 minutes

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

Frequently asked questions

What is Nitrogen pentafluoride in simple terms?

Why does Nitrogen pentafluoride 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 Nitrogen pentafluoride?

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 Nitrogen pentafluoride.