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2science t1_ivsvpp7 wrote

Reply to comment by ScootysDad in Why do neutrons tend to interact more readily with light nuclei rather than heavy ones (i.e., why is water a better neutron shield than lead)? by Calgaris_Rex

I wonder whether water is considered denser than liquid hydrogen because it's heavier.

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ccdy t1_ivtgbbo wrote

Water has a hydrogen atom number density of 111 mol/L, while that of liquid hydrogen is 70.3 mol/L. No, it's not just due to water having a higher molecular weight.

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Calixare t1_ivtxzzh wrote

So, BeH2 and liquid NH3 will be slightly better. Of course, applying water is much easier.

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ScootysDad t1_ivvp1bu wrote

The BeH2 molecule has a very linear structure with the H atoms bonded "inline" so they cannot be as densely packed as H2O. Further, it's actually a solid and form a kind of crystalline (lots of open space). NH3 (amonia) bonding is something vague for me but I think it has something to do with the electron orbital in O that give is a higher charge than N thus allowing it to be more attractive than N in that configuration. I don't think it comes even close.

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Calixare t1_ivwo620 wrote

But they do. Respectively, 118 and 120 mol H per L.

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