4 ms·

I'm confused. The article is about how various excited states of tin are generated. But tin is atomic number 50, platinum and gold are 78 and 79 respectively.

by mcswell 6mo ago

I'm confused. The article is about how various excited states of tin are generated. But tin is atomic number 50, platinum and gold are 78 and 79 respectively. Can someone draw a line between these?

bonzini 6mo ago
It's about refining theoreticals models that are used to predict nucleosynthesis of heavier elements. The researchers used indium because we can obtain the required neutron-heavy isotopes for indium but not for heavier elements such as gold or platinum. But improving the model with data from indium, they say, makes it more accurate for gold as well? Why then gold in the title? Probably just because it's shiny.
- adrian_b 6mo ago
  Platinum is also a peak of element abundance, together with its neighbor elements. So any model of how the elements have been produced must explain why the probability of making platinum and its neighbor elements, osmium, iridium and gold was higher than the probability of making other elements. The existence of other abundance peaks is easier to understand, e.g. the peaks at tin and at lead happened because these 2 metals have "magic" numbers of protons, i.e. 50 and 82, which correspond to complete nucleon layers. The peak at platinum is higher to understand, so to explain it you need accurate models. On Earth it is not obvious that the heavy platinum-group metals and gold are located on an abundance peak, because all these precious metals have gone deep inside the Earth, into its iron core, so the crust of the Earth is depleted in them, which has made them rare and precious. There are asteroids where the iron cores are easily accessible and they contain great amounts of platinum and related metals. However, the idea that mining that would be easy is extremely naive. On Earth, mining gold and platinum is easy, because they do not mix with silicate rocks so they can be found as native metals or sulfides/arsenides/tellurides that can be easily separated from silicate rocks and then the metals are easy to extract. On the other hand, in asteroids platinum and the other precious metals are dissolved in iron uniformly, so they are extremely diluted, in proportions of less than 1 part per million. Therefore, even if the total amount of platinum and gold is huge, concentrating one gram of platinum from one ton of iron would be tremendously difficult, requiring a huge amount of energy. Mining asteroids for the purpose of bringing something back to Earth will certainly not happen before solving much easier problems, e.g. growing back an amputated leg or any other part of the body. The fact that at least a startup exists that claims to work to achieve such mining is just a certain scam with no other goal than mine money from naive investors.
  - holoduke 6mo ago
    I thought the impact of Thea made heavier elements spread much more evenly towards the surface.
    - adrian_b 6mo ago
      True, but even with that, the amount of siderophile elements like platinum and gold in the crust is much less than in the core of the Earth ("siderophile" means that at the contact between molten iron and molten silicate rock such elements go into the molten iron). Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust.
      - adolph 6mo ago
        > Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust. Wow, its wild to think of a counterfactual world without gold. Would those metals have emerged to the crust from volcanism or is that material not sourced deeply enough?
        adrian_b 6mo ago
        Volcanism at most brings material from the upper mantle, but usually such material becomes mixed with material from the crust, while ascending. The mantle has slightly bigger concentrations of precious metals than the crust, but the concentrations remain many times smaller than in the core. The reason is that both the mantle and the crust are made mostly of silicate rocks. The mantle is made of heavy silicate rocks and the crust is made of light silicate rocks, which float on the denser mantle. The metals that are resistant to oxidation do not mix well with silicates, so they tend to segregate from them, and then, being heavier than rocks, they tend to descend towards the core. If they reach the core, then they dissolve into the melted iron. When lava is expelled by volcanism, the precious metals contained in it usually separate from the silicates together with metal sulfides and arsenides, which makes them easier to find than if they were dispersed uniformly in the rocks. Other elements that ere much more abundant, for instance germanium and gallium, are harder to mine than the precious metals because they are not concentrated in distinct minerals but they are uniformly distributed in many rocks.

by mcswell 6mo ago

I'm confused. The article is about how various excited states of tin are generated. But tin is atomic number 50, platinum and gold are 78 and 79 respectively. Can someone draw a line between these?

bonzini 6mo ago

It's about refining theoreticals models that are used to predict nucleosynthesis of heavier elements. The researchers used indium because we can obtain the required neutron-heavy isotopes for indium but not for heavier elements such as gold or platinum. But improving the model with data from indium, they say, makes it more accurate for gold as well? Why then gold in the title? Probably just because it's shiny.

adrian_b 6mo ago
Platinum is also a peak of element abundance, together with its neighbor elements. So any model of how the elements have been produced must explain why the probability of making platinum and its neighbor elements, osmium, iridium and gold was higher than the probability of making other elements. The existence of other abundance peaks is easier to understand, e.g. the peaks at tin and at lead happened because these 2 metals have "magic" numbers of protons, i.e. 50 and 82, which correspond to complete nucleon layers. The peak at platinum is higher to understand, so to explain it you need accurate models. On Earth it is not obvious that the heavy platinum-group metals and gold are located on an abundance peak, because all these precious metals have gone deep inside the Earth, into its iron core, so the crust of the Earth is depleted in them, which has made them rare and precious. There are asteroids where the iron cores are easily accessible and they contain great amounts of platinum and related metals. However, the idea that mining that would be easy is extremely naive. On Earth, mining gold and platinum is easy, because they do not mix with silicate rocks so they can be found as native metals or sulfides/arsenides/tellurides that can be easily separated from silicate rocks and then the metals are easy to extract. On the other hand, in asteroids platinum and the other precious metals are dissolved in iron uniformly, so they are extremely diluted, in proportions of less than 1 part per million. Therefore, even if the total amount of platinum and gold is huge, concentrating one gram of platinum from one ton of iron would be tremendously difficult, requiring a huge amount of energy. Mining asteroids for the purpose of bringing something back to Earth will certainly not happen before solving much easier problems, e.g. growing back an amputated leg or any other part of the body. The fact that at least a startup exists that claims to work to achieve such mining is just a certain scam with no other goal than mine money from naive investors.
- holoduke 6mo ago
  I thought the impact of Thea made heavier elements spread much more evenly towards the surface.
  - adrian_b 6mo ago
    True, but even with that, the amount of siderophile elements like platinum and gold in the crust is much less than in the core of the Earth ("siderophile" means that at the contact between molten iron and molten silicate rock such elements go into the molten iron). Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust.
    - adolph 6mo ago
      > Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust. Wow, its wild to think of a counterfactual world without gold. Would those metals have emerged to the crust from volcanism or is that material not sourced deeply enough?
      - adrian_b 6mo ago
        Volcanism at most brings material from the upper mantle, but usually such material becomes mixed with material from the crust, while ascending. The mantle has slightly bigger concentrations of precious metals than the crust, but the concentrations remain many times smaller than in the core. The reason is that both the mantle and the crust are made mostly of silicate rocks. The mantle is made of heavy silicate rocks and the crust is made of light silicate rocks, which float on the denser mantle. The metals that are resistant to oxidation do not mix well with silicates, so they tend to segregate from them, and then, being heavier than rocks, they tend to descend towards the core. If they reach the core, then they dissolve into the melted iron. When lava is expelled by volcanism, the precious metals contained in it usually separate from the silicates together with metal sulfides and arsenides, which makes them easier to find than if they were dispersed uniformly in the rocks. Other elements that ere much more abundant, for instance germanium and gallium, are harder to mine than the precious metals because they are not concentrated in distinct minerals but they are uniformly distributed in many rocks.