chemistry

Phosphide

Phosphide 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 Phosphide rather than just read about it. In short: In chemistry, a phosphide is a compound containing the P3− ion or its equivalent. Many different phosphides are known, with widely differing structures.

Key takeaways

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

Reference excerpt

In chemistry, a phosphide is a compound containing the P3− ion or its equivalent. Many different phosphides are known, with widely differing structures. Most commonly encountered on the binary phosphides, i.e. those materials consisting only of phosphorus and a less electronegative element. Numerous are polyphosphides, which are solids consisting of anionic chains or clusters of phosphorus. Phosphides are known with the majority of less electronegative elements with the exception of Hg, Pb, Sb, Bi, Te, and Po. Finally, some phosphides are molecular.

Binary phosphides Binary phosphides include phosphorus and one other element. An example of a group 1 phosphide is sodium phosphide (Na3P). Other notable examples include aluminium phosphide (AlP) and calcium phosphide (Ca3P2), which are used as pesticides, exploiting their tendency to release toxic phosphine upon hydrolysis. Magnesium phosphide (Mg3P2) also is moisture sensitive. Indium phosphide (InP) and gallium phosphide (GaP) are used as a semiconductors, often in combination of related arsenides. Copper phosphide (Cu3P) illustrates a rare stoichiometry for a phosphide. These species are insoluble in all solvents – they are 3-dimensional solid state polymers. For those with electropositive metals, the materials hydrolyze:

Ca3P2 + 6 H2O → 3 Ca(OH)2 + 2 PH3

Polyphosphides

Polyphosphides contain P−P bonds. The simplest polyphosphides would be derivatives of P4−2. The free anions are rarely encountered because they are so basic. Most members follow the octet rule. Well studied polyphosphides are derivatives of P3−7. This Zintl cluster anion is obtained with diverse alkali metal derivatives. The nomenclature for polyphosphides can be deceptive. As confirmed by X-ray crystallography tin triphosphide and germanium triphosphide are not triphosphides, but hexaphosphides. They consist of ruffled cyclo-P6−6 subunits. Another example of deceptive nomenclature is "thorium pentaphosphide", which consists of a polymeric polyphosphide related to Hittorf's phosphorus.

Several polyphosphides contain the cluster P3−11 ions and polymeric chain anions (e.g. the helical (P−)n ion) and complex sheet or 3D anions. The range of structures is extensive. Potassium has nine phosphides: K3P, K4P3, K5P4, KP, K4P6, K3P7, K3P11, KP10.3, KP15. Eight mono- and polyphosphides of nickel also exist: (Ni3P, Ni5P2, Ni12P5, Ni2P, Ni5P4, NiP, NiP2, NiP3). Two polyphosphide ions, P4−3 found in K4P3 and P5−4 found in K5P4, are radical anions with an odd number of valence electrons.

Preparation of phosphide and polyphosphide materials There are many ways to prepare phosphide compounds. One common way involves heating a metal and red phosphorus (P) under inert atmospheric conditions or vacuum. In principle, all metal phosphides and polyphosphides can be synthesized from elemental phosphorus and the respective metal element in stoichiometric forms. However, the synthesis is complicated due to several problems. The exothermic reactions are often explosive due to local overheating. Oxidized metals, or even just an oxidized layer on the exterior of the metal, causes extreme and unacceptably high temperatures for beginning phosphorination. Hydrothermal reactions to generate nickel phosphides have produced pure and well crystallized nickel phosphide compounds, Ni2P and Ni12P5. These compounds were synthesized through a solid-liquid reaction between NiCl2·12H2O and red phosphorus at 200 °C for 24 and 48 hours, respectively. Metal phosphides are also produced by reaction of tris(trimethylsilyl)phosphine with metal halides. In this method, the halide is liberated as the volatile trimethylsilyl chloride.

A method for the preparation of K2P16 from red phosphorus and potassium ethoxide has been reported.

Molecular phosphides Compounds with triple bonds between a metal and phosphorus are rare. The main examples have the formula P≡Mo(NR2)3, where R is a bulky organic substituent.

Organic phosphides

Many organophosphides are known. Common examples have the formula R2PM where R is an organic substituent and M is a metal. One example is lithium diphenylphosphide.

Natural examples The mineral schreibersite (Fe,Ni)3P is common in some meteorites.

References

Illustrations

Phosphide: Close up on the structure of SnP3, highlighting the bonding around P (violet) and Sn (gray). — Close up on the structure of SnP3, highlighting the bonding around P (violet) and Sn (gray).

Worked examples

Example 1 — a first encounter with Phosphide

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

In research: Phosphide 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 Phosphide 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: Phosphide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Anions, Phosphides, Phosphorus(−III) compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Phosphide 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 Phosphide in 20 minutes

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

Frequently asked questions

What is Phosphide in simple terms?

In chemistry, a phosphide is a compound containing the P3− ion or its equivalent. Many different phosphides are known, with widely differing structures.

Why does Phosphide 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 Phosphide?

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 Phosphide.