You're pretty close there, but not quite. Just one gold atom is recognizably a gold atom for certain, but yes, in small enough groups, "funny things happen". There are a couple of reasons. For one thing, it's a pretty huge group of atoms it takes for us to perceive something with the normal senses, and in that large a group, a lot of quantum "funny business" is all averaged out. In small enough groups, that's not so true anymore. So in tiny groups, quantum weirdness has more effect as a fraction of the total. h-bar is tiny, but not infinitely tiny.
If you took chemistry, all that stuff about electron shells? Well it turns out that similar things happen anytime you get a few things together - be they electrons around a nucleus, hadrons inside a nucleus, or even a few atoms in a cluster. There is "shell like" behavior that goes on in small quantities of things, especially where the lines blur between pure classical and pure quantum behavior. If you think of a lump of solid, say a crystal - internally there are all these electron bonds that are satisfied atom to nearby atom - but what about the surface? That's where things get strange, and in a micro-cluster, it's nearly all surface area, so it's nearly all "funny" - dangling bonds, atoms that aren't quite happy where they are (can't always find the lowest energy stable state) and so on.
So there are two possible things going on with nanotech. One is that we can now put things together an atom at a time - kind of like life with proteins, we can work with "the nature of shapes" of not-quite-satisfied charges fitting like keys and locks - and we can do a lot with shapes alone. Then we can start looking at composites, or metamaterials, which can have more than one atom type involved - you can almost build a little factory, with this end of the thing being "attractive" to a feed material, but shoving it "down the assembly line" to a place where the stronger fields of unsatisfied charge might take it apart - or force a hole to add something - so now it doesn't "fit" anymore and gets ejected back out into the world, changed.
That's the nature of catalysis, for one thing. So far, most of the interesting catalysts have been PMs (but not all). Things like Pt and Pd have a fairly unique surface patter of charge that make this so, along with being useful because they are "noble".
But - you could call that an accident of nature that these particular pure substances are the best so far - with what science is looking into now (not very smart or keeping on topic with it) - a whole new world is appearing there for catalysis possibilities, and other things -
like my post here about Maxwell's demon. But this one was interesting because it used PM's other than the big two for catalysis, and one of the reasons for using gold was its large size of atom. But that's not to say lead wouldn't work for some things, or any other large atom for that matter.
So catalysis might be making some huge leaps in the next decade or so from nanotech, and that's a big deal and will affect markets.
Another place that might see huge changes from nanotech or metamaterials is permanent magnets, as they are actually still fairly poorly understood. That of course is what's currently driving the RE markets. That could change overnight if a new arrangement of cheaper atoms gives the same or better results, and no theory says that can't happen at this point.
Right now, the stumbling block is that there's no feedforward theory of this at present, and that these custom atomic arrangements don't just fall together in a test tube - they're hard to make at all, much less in mole quantities, at present. In some cases, this is changing as polymerization and other tricks are brought to bear, however. We just can't do really complex stuff auto-assembled yet, life still rules in that area for now. But we are learning how life manages it...
Hope that gets it for an answer. To be short, yes, clusters of one atom can act kind of like a super atom with properties different from the individual ones - it's all that shell stuff happening on a slightly larger scale again - Pauli's exclusion principle, once you understand it for real, explains it all - and it takes awhile to get that one in your head. Hint - it's not magic forces, it's
geometry of the "shells" which aren't round - they are things like dipoles, quadrupoles and so on...which is why two can't be in the same space identically, they won't "fit". But you can have a dipole in all of X, Y, Z axes at the same time-place, because the wavefunction has zero value at the origin, so they "fit" that way. Which explains why there are thus many electrons in the first shell (two per axis, as they can be spin up or down per). When you work this out, all the "magic numbers" just fall out of it geometrically, and with slight mods due to protons etc having some different quantum numbers possible, the same applies for stable nuclei as well - very strange how the world is assembled.
Sadly, I know jack squat about this, really, but even more sadly, I think I know more than most of the scientists studying the stuff in the link! Most of them are so specialized that most of the time they are just rediscovering what's been known a long time in some other specialty. I try to be a generalist, but it's a lotta work.
There's a lot to learn about that fuzzy boundary between "pure classical" and "pure quantum" that the math really doesn't handle well at all - we know it works well in the pure cases, but at the transition no one's really worked out how to splice the equations together very well, and we still don't have squat "feed forward" for that or much of anything else. So we try stuff, then try to use the math to explain it, not the other way around, as it would be nicer to have it.
Edit, I have a really good article with pix of the odd things about nano clusters somewhere in an old Physics today - if I find, it, I'll scan and republish it. It's pretty cool stuff.
It's not that it isn't gold till you have a bunch of it, it's that gold (or anything else) acts differently in small clusters than it does in bulk. And the differences can be real interesting. Sodium for example, is electropositive as can be in bulk -even takes water apart. But in small clusters, some cluster sizes act electronegative - like chlorine...cool stuff like that. Still sodium the entire time, strip off one atom, it's a sodium atom, or put enough together and get bulk sodium. Most of the interesting effects happen between about 4 and about 20 atoms, larger and bulk properties start to appear, like normal, and too small doesn't allow for much complexity. Mother nature can count!
