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ECatPlay t1_j7e842q wrote

Sure, it's called a Chart of the Nuclides or Table of the Nuclides. Instead of being organized with similar chemical properties in a column, it is organized based on the number of protons and number of neutrons, in columns for one and rows for the other. There are a couple of orientations used. Wikipedia has a Full Table that starts with hydrogen in the upper left, and is oriented using columns for each element (with increasing atomic number going to the right), and rows for each number of neutrons (for the different isotopes of each element) going down.

A full table like this is fine on a wall chart, but it's easier to navigate online. Entering the atomic symbol and isotope mass number in this Chart of the Nuclides, for instance. Entering "Cl" and "35" for chlorine, for example, takes you right to ^(35)Cl. This table uses the other common orientation: with hydrogen in the lower left, increasing atomic number in each row going up, and increasing number of neutrons in each column going to the right. More like a standard X and Y plot.

This layout is convenient for nuclear physicists, in that (among other things) it's easy to relate the starting atom to the result of a nuclear process. Beta decay (loss of an electron), for instance, would transform one of the neutrons in an atom into a proton, increasing the atomic number but not the mass. This corresponds to just moving diagonally up one row and to the left one column in the Chart of the Nuclides: up to ^(35)Ar from ^(35)Cl in our chlorine example. (Not that this is a highly probable event, in the case of ^(35)Cl). And radioactive decay with neutron emission takes you one column to the left in the same row: ^(34)Cl from ^(35)Cl. And Alpha radiation (emission of a helium nucleus, 2 neutrons and 2 protons) is just moving diagonally down 2 rows and left 2 columns: ^(31)P from ^(35)Cl.

But you asked this as a Chemistry question, and although it's periodicity is not related to chemical behavior, it does bring out the role of isotopes in chemistry. For instance, we're used to thinking of the molecular weight of an element as the sum of protons and neutrons. But the molecular weight given for chlorine in the Periodic Table of the Elements, 35.453, is not an integer. So at first this may seem odd. But the chlorine row in the Chart of the Nuclides brings out the fact that elemental chlorine is a mixture of isotopes, mostly ^(35)Cl and ^(37)Cl, with a natural abundance of 76% for ^(35)Cl and 24% for ^(37)Cl. And this averages out to the molecular weight of 35.453 in naturally occurring chlorine.

Another chemical consideration where understanding the isotopes helps, is in interpreting Mass Spectra. When chlorine is present in a chemical being sampled for instance, since 76% of the time the chlorine atom will be ^(35)Cl and 24% of the time it will be ^(37)Cl, this will show up as very characteristic pairs of peaks in a 3:1 ratio, 2 mass units apart in all chlorine containing fragments in the Mass Spectrum. This is a big help in the interpretation of fragmentation patterns.

(Edit: got my directions crossed)

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NotAPreppie t1_j7e8rds wrote

I still have this book from my nuclear chemistry class almost a decade ago.

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openly_gray t1_j7eel8b wrote

Thanks for the link. While I have no direct use of it its nonetheless quite interesting to look at the nuclide distribution and half-life

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RadioactiveHop t1_j7erqhi wrote

There is also the IAEA Isotope Browser app you can install on your smartphone (Android at least)

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princeofgonville t1_j7fbdof wrote

(a) this is fascinating and will distract me all day from what I was supposed two be doing.

(b) how come I didn't learn about this at school? (I did both chemistry and physics - was I not paying attention?)

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zekromNLR t1_j7hqalm wrote

> When chlorine is present in a chemical being sampled for instance, since 76% of the time the chlorine atom will be 35Cl and 24% of the time it will be 37Cl, this will show up as very characteristic pairs of peaks in a 3:1 ratio, 2 mass units apart in all chlorine containing fragments in the Mass Spectrum.

Though that would only be for fragments containing a single chlorine atom each, right? Something with two or three chlorine atoms in one fragment should show a much more complex pattern, since each chlorine atom can either be 35Cl or 37Cl.

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ECatPlay t1_j7ima7e wrote

Oh sure! If there were two chlorines present in the chemical, then any fragments in the mass spec that contained 2 chlorines would appear as a triplet of peaks, 2 mass units apart, in the ratio 0.578:0.365:0.058 (if I did the math correctly, 0.76x0.76:2x0.76x0.24:0.24:0.24). So it would be easy to distinguish between fragments with one chlorine or with two chlorines: the characteristic triplet would mean 2 chlorines and the doublet would mean one.

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[deleted] OP t1_j7hurcs wrote

Oh gosh, this is the direction I was going! This is very neat, and I big appreciate the answer! Thank you!

I do have a question. To quick preface, my life is Lifing™ right now, so apologies if this is not very clear or based on correct thinking.

I recently came to learn about muonium. Recognizing both muonium is a recent development, and that it is fairly "exotic" in its components, I am curious about where it would end up on the table of nuclides. Using Wikipedia's table for simplicity, the top left "Z→" indicates the atomic number (right?) and thus, in ordinary matter, the number of protons (yes?). Does (or would) the atomic number of muonium equal to that of hydrogen then (in that although there are no protons, the charge of both is the same)? In short, this question is trying to ask how would muonium plug into the table?

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Michkov t1_j7i7sm4 wrote

Problem is it wasn't designed to display fractions of proton masses. What gives it that pixelated look is that each isotope has an integer coordinate, since its coordinates are defined via number of nucleids vs number of protons.

Now the muon is only 11% of the proton mass, so that breaks the nice grid pattern. It also has a charge of -1 so that doesn't really correspond to the protons charge of +1.

You could modify the table, so the axis are total mass vs electrical charge. In that scheme muonium would go below the neutron line.

PS: Here is an interactive version of the table

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