Re: Roses' metal an amalgam- what gives it so low a melting point?

I had never come across Rose's metal until I saw this question. I now know it is a fusible alloy consisting of 50 per cent bismuth, 25 percent lead and 25 per cent tin. That makes it sound like a type of solder.

Your question gives no detail about what exactly you want to know. If the following explanation is too general, then you could re-submit the question and see if someone else can answer it.

Metals at the bottom of groups 4 and 5 tend to have low melting points because of the large size of the atoms and the few valence electrons given up into the bonding orbital ("sea of electrons"). Typically, the s² electrons are not released, giving these metals a valency of 2 (Pb, Sn) or 3 (Bi). The resulting metal ions have a low charge density, giving relatively weak metallic bonding and low melting points. When the metals are alloyed, the melting point is even lower, due to disruption of the packing caused by the different sized atoms. This is why solder melts so easily - it is an alloy of low melting point metals.