[Stibnut]

I've done quite a bit of home chemistry experimentation over the past year or so, but I got a knock on the door from some friendly FBI agents who wanted to know what I was doing with all the chemicals and glassware. Turns out Big Brother gets a little suspicious when people make repeated ebay chemical purchases. Luckily they didn't press charges, but they did call the fire department, which forced me to get rid of everything interesting. Luckily my element collection and radioactives survived, though.

So it's back to basics for me. I've been playing around with some element samples from my collection, and I have a really basic classification question. Arsenic, antimony, and bismuth all seem to behave roughly the same to me: they're all soft, crumbly and extremely brittle, they all appear metallic, and all of them conduct electricity (poorly, but better than e.g. graphite, and far better than semiconductors). Electrical conductivity even decreases as you go down: As is a better conductor than Sb which is in turn better than Bi. Melting points are fairly low for all of them but lowest for bismuth.

Yet it seems that, more or less universally, Bi is considered a metal while As and Sb are metalloids. Why is this? Is there any property in which Bi shows much more metallic character than Sb?

To be clear, the amount of As I've been playing with have been no more than 2 g, (nearly) all of which made it back in the vial. But I have ~50 g chunks of Sb and Bi, and they're as similar to each other as I've ever seen two metals be.

[Borek]

It is not only about physical properties, but also about chemical properties, and Bi is a bit more "metallic" in its behavior than the As and Sb.

That being said this classification (as many others) are our attempts at dealing with nature - and nature doesn't care. We try to classify elements as metals, non-metals and metalloids, but it is not easy to draw a precise line when there is kind of a continuum of properties.

[Arkcon]

Yet it seems that, more or less universally, Bi is considered a metal while As and Sb are metalloids. Why is this? Is there any property in which Bi shows much more metallic character than Sb?

What properties have you found in your lumps?  Can you build a table of them for us and show us how you compare them to each other?