Lightest metal

[Birt]

HI Abers
I know lithium is the lightest metal known but a friend of mine says certain alloys can be lighter. Is this correct? If so then how can 2 heavier metals be alloyed to make a metal lighter than both components?

[Catso]

Sounds fundementally wrong to me.

You can probably make lighter components from the alloy, because it may well be stronger than any of the constituents individually.

[qapmoc]

Maybe you can make a foamed alloy containing bubbles = lighter.

[ryepie]

Only one of the elements in an alloy has to be metal, not all of them. So in theory if your comparison is based on identically-sized samples (in terms of moles) then I would have thought an alloy of, say, lithium-oxygen (I'm not saying this exists...it probably doesn't!) would be lighter than pure lithium. If your friend is talking about an alloy, all of whose constituents are metals, then I would say he's fibbing!

[ryepie]

I should also add that the lightest metal you will EVER get is metallic hydrogen, although this is only found in the middle of large planets, such as Jupiter and Saturn.

[theprof]

Hi Birt

Lithium has a density of 0.53g per cubic centimetre.

I'll think you'll find that the lowest density alloys are amongst the magnesium alloys where the density range is typically between 1.75 and 1.85g per cubic centimetre. These are the lightest alloys that can be die-cast and used structurally. I can't remember the code numbers offhand.

So yes, I think your friend was fibbing. As far as qapmoc's suggestion goes, unfortunately, what works for Aero chocolate bars does not work for alloys!

There have been what you might loosely call alloys produced under laboratory conditions over the last few years which have a slightly lower density than magnesium alloys. All the same, I think it's unlikely your friend would be familiar with them.

[mizz_x_melik]

What is the lightest metal