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this is a gold bar. If we look at its structure, will we see that there are atoms that have a different number of neutrons (aka isotopes) (as far as I'm concerned, an isotope is an atom with a different amount of neutrons in it) or has it to be another bar that consists of this isotopes?

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  • $\begingroup$ Gold has only one naturally occuring isotope: 197-Au. $\endgroup$ – Ed V Aug 31 '19 at 12:37
  • $\begingroup$ Ed V, what about others, do people make them? (and thank you, a lot) And 197-Au consists of atoms that have the same number of neutrons, right? $\endgroup$ – Lucos Aug 31 '19 at 12:45
  • $\begingroup$ Sure! Wikipedia (check it out!) shows 4 major synthetic gold isotopes and my guess is that there are more. The 197-Au has 79 protons and 118 neutrons. $\endgroup$ – Ed V Aug 31 '19 at 12:51
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    $\begingroup$ @EdV Maybe you know it, maybe of interest for you / colleagues of you / users of ChemSE: the Karlsruhe nuclide map's review about its current 10th edition / 2018 (open access here: doi.org/10.1051/epjn/2019004) and an elder review, including context to other maps, here: www.nucleonica1.com/wiki/images/9/96/NuclearData_FTU_2013.pdf). $\endgroup$ – Buttonwood Aug 31 '19 at 18:45
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    $\begingroup$ @EdV Then take these as little «thank you» for hinting in one of your answers or comments somewhere in the second quarter of 2019 -- I don't recall the exact spot -- to the work by Joel Tellinghuisen around how to process and apply statistics on experimental data in chemistry and calibration / regression curves. It wasn't taught this way in the classes I attended, and often, a point to reflect how to do better. $\endgroup$ – Buttonwood Aug 31 '19 at 23:01
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Gold has only one natural isotope: 197. There are artificial gold isotopes, but they do not end up in gold bars. Even if they did, their half life is measured in days so don’t expect much to remain after a year or so.

The “structure” of the metal bar, or atomic arrangement, has nothing to do with its isotopic composition.

Even if you were to measure somehow trace amounts of radioactive gold in your bar (for example gold-195) using methods such as mass spectrometry, it would be hard to distinguish from platinum-195, a very common impurity in gold. To complicate it even more, you will not know whether the Pt-195 was there to begin with, or formed by the decay of Au-195.

If you had a gold bar made of pure gold-195, you would be dead soon from radiation sickness unless you took the appropriate safety measures.

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    $\begingroup$ A 1 kg gold bar of pure Au-195 in 0.5 m working distance gives a dose rate of about 24 Sv/h. So first symptoms of sickness would occur after about half an hour. If you then stop working with it, you would die in about one week. Anyway, the bar would be red hot since it's releasing about 2.7 kW of isotopic power. $\endgroup$ – Faded Giant Aug 31 '19 at 15:01

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