chemistry

Isotopes of promethium

Isotopes of promethium 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 Isotopes of promethium rather than just read about it. In short: Promethium (61Pm) is an artificial element, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes.

Key takeaways

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

Reference excerpt

Promethium (61Pm) is an artificial element, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was first synthesized in 1945. Like technetium, it is preceded and followed by elements with stable isotopes. The known isotopes run from 128Pm to 166Pm, 39 in all; the most stable are 145Pm with a half-life of 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm (the common isotope) with a half-life of 2.6234 years. 143Pm and 144Pm also have lengthy if poorly-known lives on the order of a year, but all the others have half-lives that are less than six days, with the majority less than a few minutes. There are also 24 known meta states with the most stable being 148mPm at a half-life of 41.29 days. The primary decay mode for isotopes lighter than 146Pm is electron capture resulting in isotopes of neodymium, and the primary decay mode heavier than 146Pm is beta decay giving isotopes of samarium; promethium-146 itself decays both ways.

List of isotopes

Stability of promethium isotopes

Promethium is one of the two elements of the first 82 elements that has no stable isotopes. This is a rarely occurring effect of the liquid drop model. Namely, promethium does not have any beta-stable isotopes, as for any mass number, it is energetically favorable for a promethium isotope to undergo positron emission or beta decay, respectively forming a neodymium or samarium isotope which has a higher binding energy per nucleon. The other element for which this happens is technetium (Z = 43).

Promethium-147 Promethium-147 beta decays to the long-lived primordial radioisotope samarium-147 with a half-life of 2.6234 years, emitting low-energy beta radiation without gamma emission. It is a common fission product, produced in nuclear reactors and in trace quantities in nature, where it is also produced by the alpha decay of europium-151. In the reactor environment, it is almost exclusively produced through beta decay of neodymium-147 as usual for fission products. The isotopes 142-146Nd, 148Nd, and 150Nd are all stable with respect to beta decay, so the isotopes of promethium with those masses are not produced by beta decay and are therefore not significant fission products (as they could only be produced directly, rather than through a beta-decay chain). 149Pm and 151Pm are, but have half-lives of only 53.08 and 28.40 hours, so are not found in spent nuclear fuel that has been cooled for months or years. Promethium-147 is used as a beta particle source and a radioisotope thermoelectric generator (RTG) fuel; its power density is about 2 watts per gram. Mixed with a phosphor, it was used to illuminate the Apollo Lunar Module electrical switch tips and the control panels of the Lunar Roving Vehicle. For luminescent applications, it has generally been replaced by tritium, which is even safer and has a longer half-life (12.32 years).

See also Daughter products other than promethium

Isotopes of samarium Isotopes of neodymium Isotopes of praseodymium

References

Worked examples

Example 1 — a first encounter with Isotopes of promethium

Start with the simplest possible case. Write down what Isotopes of promethium 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 Isotopes of promethium 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 Isotopes of promethium 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 Isotopes of promethium

In research: Isotopes of promethium 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 Isotopes of promethium 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: Isotopes of promethium is common in secondary-school and first-year university syllabi. It links to neighbouring topics Isotopes of promethium, Lists of isotopes by element, Promethium, so understanding it makes those chapters shorter.
In everyday life: Look for Isotopes of promethium 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 Isotopes of promethium in 20 minutes

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

Frequently asked questions

What is Isotopes of promethium in simple terms?

Why does Isotopes of promethium 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 Isotopes of promethium?

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 Isotopes of promethium.