Because they are atoms. You need high energy to squeeze them together and they give off large energy when they do squeeze together.

Not from want of trying.

Research alchemy.

Alchemy

Edited by me.

Because what constitutes an element is not the arrangement of atoms, but the structure of atoms, e.g., how many protons there are in the atom’s nucleus.
To add protons to an atom requires pin point accuracy, which we do not have, and it requires massive amounts of energy to overcome the repulsive forces. We are talking about nuclear fusion.
And to remove protons from a nucleus is equally tricky. You have to split it, which means you have to bombard it with neutrons to break the very strong nuclear bonding force.
Needs a lot of energy, and the result is usually impure, because the resulting nucleus fragments generally are of unequal sizes.
You can generate gold this way in either particle accelerators and nuclear reactors, but the problems with that are:
1. You need specific raw materials, either mercury, or platinum. platinum is more valuable than gold, so scratch that, and with mercury, only a small % of naturally occuring mercury is the right isotope able to be converted into gold.
2. Takes a lot of energy and is expensive, because of the raw materials and the machinery
3. The resulting gold will be radioactive.

Scientists and materials researchers do move atoms around to create new molecules, and hence new materials, metal alloys and plastics especially. But those are not atomic changes.

You’re asking about changing the nature of one atom to become a different atom, which is a much finer degree of change, as it requires adding or deleting neutrons, protons and electrons at the atomic level, at least following current atomic theory. Not only would those changes require massive amounts of energy, as @Imadethisupwithnoforethought and @ragingloli state, but we’re not even sure how to make those changes.

Given the current state of technology, even assuming the possibility for success, which is far from assured, the cost in terms of energy expended would make it non-commercial, at least for the foreseeable future.

I don’t want to imply that it is impossible. We use Fission bombs(like Nagasaki and Hiroshima style bombs) which turn Uranium into lighter elements to set off Hydrogen Fusion, which turns Hydrogen into Helium and heavier elements. I just want you to consider how large the forces involved are to do these simple conversion tasks, and the energy inputs and releases involved.

Asimov had an interesting take on this.

This article may help: http://en.wikipedia.org/wiki/Synthesis_of_precious_metals#Gold

As @ragingloli wrote the gold created in 1924 and 1941 was radioactive.

The fusion of iron and hydrogen requires energy, as does everything from cobalt to platinum in order to create gold.

The fission of everything from mercury to uranium into gold doesn’t require energy, it actually produces energy. However, building the machinery to achieve this is still very expensive.

Perhaps, some day we could use radon and make it emit alpha particles, lose some neutrons and change one neutron into a proton to make gold…

Yeah I second the other jellies who mentioned Alchemy, that’s what you’re talking about.

Today, of course the pursuit continues, albeit with more science and less “magic and mysticism”.

However, given the world’s situation it is becoming more desirable to synthesize materials such as blood, tissues and other organic materials than minerals. I mean, if you could “make” precious metals, how precious would they be really? A lab-grown heart on the other hand, is precious no matter how many you make.

They can.
But it’s expensive, way too expensive to make it worth doing instead of finding the target elements.

As everyone who mentioned fission or fusion note, that’s what’s going on in those processes.
Those both involve expensive specialized machinery and involve a LOT of energy (=danger).

Can we now transmute base substances into gold? (The Straight Dope, 2012)

@buckyboy28 ”...why can’t atoms be rearranged and reconstituted into other elements…?” An atom’s identity as a particular element is determined entirely by its nucleus, not by how the atoms are arranged. Rearranging atoms is usually called chemistry, which also describes the results of alchemy.

You could rearrange particles in the atomic nucleus using nuclear reactors, as explained in the above article, though it appears that making non-radioactive gold is extremely difficult. Not sure about other precious metals.