chemistry

Irving–Williams series

Irving–Williams series 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 Irving–Williams series rather than just read about it. In short: The Irving–Williams series refers to the relative stabilities of complexes formed by transition metals. In 1953 Harry Irving and Robert Williams observed that the stability of complexes formed by divalent first-row transition metal ions generally increase across the period to a maximum stability at copper: Mn(II) < Fe(II) < Co(II) < Ni(II) < Cu(II) > Zn(II).

Key takeaways

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

Reference excerpt

The Irving–Williams series refers to the relative stabilities of complexes formed by transition metals. In 1953 Harry Irving and Robert Williams observed that the stability of complexes formed by divalent first-row transition metal ions generally increase across the period to a maximum stability at copper: Mn(II) < Fe(II) < Co(II) < Ni(II) < Cu(II) > Zn(II). Specifically, the Irving–Williams series refers to the exchange of aqua (H2O) ligands for any other ligand (L) within a metal complex. In other words, the Irving–Williams series is almost exclusively independent of the nature of the incoming ligand, L. The main application of the series is to empirically suggest an order of stability within first row transition metal complexes (where the transition metal is in oxidation state II). Another application of the Irving–Williams series is to use it as a correlation "ruler" in comparing the first stability constant for replacement of water in the aqueous ion by a ligand.

Explanation Three explanations are frequently used to explain the series:

The ionic radius is expected to decrease regularly from Mn(II) to Zn(II). This is the normal periodic trend and would account for the general increase in stability. The crystal field stabilization energy (CFSE) increases from zero for Mn(II) to a maximum at Ni(II). This makes the complexes increasingly stable. CFSE for Zn(II) is zero. Although the CFSE of Cu(II) is less than that of Ni(II), octahedral Cu(II) complexes are subject to the Jahn–Teller effect, which affords octahedral Cu(II) complexes additional stability. However, none of the above explanations can satisfactorily explain the success of the Irving–Williams series in predicting the relative stabilities of transition metal complexes. A recent study of metal-thiolate complexes indicates that an interplay between covalent and electrostatic contributions in metal–ligand binding energies might result in the Irving–Williams series. Some actual CFSE values for octahedral complexes of first-row transition metals (∆oct) are 0.4Δ (4 Dq) for iron, 0.8Δ (8 Dq) for cobalt and 1.2Δ (12 Dq) for nickel. When the stability constants are quantitatively adjusted for these values they follow the trend that is predicted, in the absence of crystal field effects, between manganese and zinc. This was an important factor contributing to the acceptance of crystal field theory, the first theory to successfully account for the thermodynamic, spectroscopic and magnetic properties of complexes of the transition metal ions and precursor to ligand field theory. Natural proteins' affinities for metal binding also follow the Irving–Williams series. However, in a recent study published in the journal Nature, researchers have reported a protein-design approach to overcome the Irving-Williams series restriction, allowing proteins to bind other metals over copper ions vice versa to Irving–Williams series.

References

External links Irving-Williams Series - Transition Metal Chemistry

Worked examples

Example 1 — a first encounter with Irving–Williams series

Start with the simplest possible case. Write down what Irving–Williams series 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 Irving–Williams series 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 Irving–Williams series 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 Irving–Williams series

In research: Irving–Williams series 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 Irving–Williams series 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: Irving–Williams series is common in secondary-school and first-year university syllabi. It links to neighbouring topics Equilibrium chemistry, Transition metals, so understanding it makes those chapters shorter.
In everyday life: Look for Irving–Williams series 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 Irving–Williams series in 20 minutes

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

Frequently asked questions

What is Irving–Williams series in simple terms?

Why does Irving–Williams series 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 Irving–Williams series?

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 Irving–Williams series.