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mfb- t1_jca0ls4 wrote

Reply to comment by Dd_8630 in Radon is a monatomic gas, but its decay products are solids. After a decay, what happens to the individual atoms of the daughter elements? Do they stay suspended in the atmosphere or slowly rain out? by foodtower

The first sentence was discussing a scenario where we only have the lead atoms (at their extremely low density) and nothing else. I added the remaining gases back in the second sentence.

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subnautus t1_jcab5bu wrote

If the scenario only takes the presence of lead into account, there's still a decent probability of lead vapor existing. You figure the vapor pressure of mercury is so well documented by experiments where ullage develops in a container filled in such a manner where no material other than mercury could be present; the same should be true of all materials subject to vacuum.

Or, put another way, your suggestion that lead would "freeze out" as soon as it hits the wall of its container suggests you could hit absolute vacuum (and thus absolute zero temperature) by simply waiting.

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mfb- t1_jcabtfm wrote

I already mentioned that, too...

> With lead alone almost all atoms would hit the wall and freeze out in milliseconds, although theoretically the vapor pressure is not zero.

The vapor pressure of lead at room temperature is absurdly small. Something below 10^(-20) Pa extrapolating from this graph.

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subnautus t1_jcaez5p wrote

3 x 10^-14 3.67 x 10^-12 Pa, actually, but I take your point.

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mfb- t1_jcalnb3 wrote

Where did that value come from?

Assuming a straight line going through (0.6, 4.6) and (1.36, -4) we reach 1000K/(293K) = 3.41 at -21.65 which means 10^(-21.6) Pa. The extrapolation that far out will come with a large uncertainty of course.

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