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6

From Pauling's "General Chemistry" (ref. 1): In 1921 the American chemist W.D. Harkins described nuclei as being built of protons and neutrons; he used the word "neutron" for a hypothetical particle with mass equal to that of the proton and with no electric charge. Ernest Rutherford made a similar suggestion during the same year. In 1932 ...


6

If you somehow magicked into existence a macroscopic solid cube of some radioisotope with a half-life in the range of minutes to hours, you would probably see the cube become blindingly white-hot then mostly vanish in less than a minute, before most of the sample has even had time to decay. Large amounts of very radioactive isotopes release enough energy to ...


5

In context of this answer, stable means not undergoing a radioactive decay, regardless of the value of measured half-life.(+) For light nuclei till about 40 nucleons, the neutron/proton ratio of stable isobars(the same nucleon count) is generally around 1.0. ( $\ce{^3He, T}$ are quite exception. ) Nuclei too aside from this ratio ( See Valley of stability ) ...


5

The heaviest water obtained with stable isotopes would be $\ce{D_2^{ 18}O}$. This compound is not well-charactetized itself, but Ref. [1] indicates that the melting point is only about 0.28°C above that of ordinary water. The implication is that overall physical properties of $\ce{D_2^{ 18}O}$ are close to those of heavy water with oxygen-16($\ce{D_2^{ 16}...


4

Of course isotopes may be separated by distillation, but it's useful, AFAIR, only for hydrogen isotopes. For uranium, gas centrifuge is proven much cheaper, to some orders of magnitude: https://ru.wikipedia.org/wiki/Газовая_центрифуга (translate this page, it contains more information than English Wikipedia article). The essence of this technology is known ...


3

Evaporation depends on molecular velocity not on the energy The simple mistake in your assumption is that evaporation is driven by molecules having enough energy to escape the liquid phase. This is wrong. Evaporation depends on whether the molecule is travelling fast enough to escape the liquid. The molecules in the liquid will have, on average, the same ...


3

Good candidates for your research would be the fallout residues of atomic bombs having exploded in the world between $1945$ and $1964$. These bombs were made by USA and the former USSR (Russia today) during the "cold war". Each time one of these superpowers had developed a "more powerful" bomb, the other one managed to create a still more ...


3

Because we can sample the environment with great precision You seem to assume that we can't know the exact makeup of a sample unless we already know the components. This is wrong. Mass spectroscopy can reliably measure the exact mass of every isotope in a sample and the relative abundance of each. If, for example, a sample of sea-water is measured, we can ...


3

Extending / reformulating Karsten Theis' answer: A probabilistic approach is to draw a tree about drawing two spheres where event $A$ (normal hydrogen, $\ce{^1H}$) dominates, but event $B$ (the next abundant isotope, $\ce{^2H}$) complements, $P(\ce{^1H} \cup{} \ce{^2H}) = 1 = \Omega{}$ and eventually to multiply the probabilities for each path (e.g., $P(\ce{^...


2

You are wrong. There are only four cases (first atom is proton or deuteron, second atom is proton or deuteron), and you have to add up two cases to get all molecules with mass number of 3, i.e. the two light blue areas in the schematic diagram below (not to scale):


2

There are different types of mass spectrometers with different modes of sample introduction, analyte ionization and ion selection/focusing. You cannot generalize "with a mass spec." In many cases of isotope ratio mass spectrometry (IRMS), compound specific isotopic analysis (CSIA), or Gas Chromatography Combustion Isotope Ratio Mass Spectrometry ...


2

Relative atomic mass is a dimensionless quantity. It is relative mass of a specie with respect to the mass of carbon-12. So the units of masses get cancelled and hence we have a 'unitless' quantity. Just like refractive index doesn't have a unit. Physical quantity that are a result of ratio don't have units as they get cancelled.


2

One possibility is Technetium-99m . According to wikipedia it is the most commonly used medical radioisotope in the world, so get your person involved in an appropriate medical procedure and you should be sorted. But you have to be a little careful what you are looking for, Technetium-99m itself decays in around 6 hours by emitting a gamma ray. But the ...


1

I finally found this book by Derek Marsh: Derek Marsh, "Spin-Label Electron Paramagnetic Resonance" (CRC Press, Boca Raton, 2019). DOI: 10.1201/9780429194634. It has many tables and the basic theory going with them. I would strongly recommend it.


1

As very simple model to find what properties are important in evaporation consider a molecule that when close to the surface moves around in a cell of side $a$ and collides with frequency $f$ into its neighbouring molecules. There is an area $a^2$ through which it can escape the surface and in a second it moves on average a distance $v= 2af$ back and forth ...


1

I would not expect significant differences in the chemical properties (reactivity) of these lead isotopes, the differences in atomic weight being as you point out very small. There are reports that claim an effect. Ref 1 for instance makes such a claim, but there is no plausible mechanism presented to explain the reported isotopic discrimination. Double ...


1

The relative entropies of two substances at a temperature $T'$ are not determined by their relative heat capacities at $T'$. Rather, $$\text {Absolute entropy at } T' \equiv S(T') =\Delta S_{0 \rightarrow T'}$$ $$= \int_{0}^{T'}\frac{\text{đ}q_{rev}}{T} = \int_{0}^{T'}\frac{C_p(T)}{T} dT.$$ I.e., for each substance, you need to consider how $C_p(T)$ varies ...


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