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Comment by johncearls | Hacker News Reader

This is a pretty basic chemistry question, but I thought someone her might be able to give a simple explanation why it seems most of these amazing catalysts are always made from precious metals. Why is it that super expensive things like gold and silver and platinum are always the backbone of these catalysts?

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The orbitals of the lowest elements on the periodic table are the largest in diameter and most flexible in bonding and rebonding.

Their ability to easily make relatively short lived bonds is the key.

These metals are often super poisonous for the same reason (heavy metal poisoning). They enter a biological system and effectively randomize a whole lot of bonds and molecules you want to be stable over decades.

By "lowest elements" do you mean elements with lowest atomic number (Hydrogen, Helium, Lithium, etc.), or closest to the bottom of a chart hanging on a wall (Rubinium, Strontium, Yttrium, etc.)?

It would seem to be the latter, given the reference to heavy metals (they probably mean noble metals more likely)

No. They are contrasting the elements operated on, mostly light elements, with heavier ones used in catalysts that are also toxic, for reasons.

Not really. It’s because of the D- orbital configuration of the coinage metal family.

Those metals are very stable and usually don’t take part in reactions as reactants, and are usually catalysts, as you already mentioned. Meaning, they let the reactants form intermediates that wouldn’t form without the catalyst. Eg by donating an electron that is given back when the reaction is complete.

If the catalyst were not stable, it would become a reactant and be consumed quickly.

Precious metal tend to not bond for very long time. Making them rather useful as catalyst. On other had my guess is that this tendency also leads them to be rare in uppermost crust of Earth as they didn't bound with other materials, but mostly sink to lower, them also being rather dense on virtue of being where they are in periodic table. This rarity is what actually makes them expensive.

I guess if it was possible to make it with common dust, they would have been discovered for long with random trial alchemist experiments, and so wouldn't look so amazingly uncommon?

Because they are themselves less likely to react permanently with any of the intermediary products or the feedstock. Think of them as 'machinery that doesn't wear out quickly' which would make them a consumable.

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