"it could be argued that it is a metal, as the traditional metal/non-metal divide passes above it. A semi-metal/metalloid at very least..."
Easy to find out, just get a lump of it and hit it with a hammer. If it flattens it's a metal, if it shatters it's a metalloid, and if it's a halogen the hammer gets oxidised.
You bring the lump of 117ium, I'll bring the hammer. And a lead suit.