Yes, but they're incredibly unstable due to being highly radioactive. We make them by firing certain atoms at a target using particle accelerators

Atoms on the periodic table are defined by the number of protons in the nucleus of the atom. It is possible to discover/create new atoms by adding new protons to a nucleus, but those large atoms tend to be very unstable (which is why we don't add them to the periodic table anymore). There is a theoretical "island of stability" when atoms get large enough, but we are nowhere near being able to create atoms that large to test.

It is possible to create new compounds or molecules from existing atoms that we have already discovered, and those new molecules could have interesting new properties.

Yes. We continue to make new elements on the heavy side of the periodic table. They are very unstable and last for very short periods of time. Some people theorise that there might be a group of very heavy elements that are stable and can exist for longer than a few seconds. This theoretical part of the periodic table is called "the island of stability."

Elements are defined by the number of protons they have, and nuclei become very unstable when they get too large, say over a hundred protons.

"New elements" would be possible under different physics, maybe; otherwise, there aren't really any "new elements."

If we're talking about theory, it's not just possible but certain that there are more elements than those listed on the periodic table. An element is defined by the number of protons in the nucleus. You can theorize a new element with 69420 protons, and that's that.

What's harder is having that new element actually exist. Elements only get on the periodic table if we can actually observe them existing. Since the middle of the last century, physicists have known how to slam atoms into each other to create heavier elements. Any element heavier than uranium does not occur naturally on Earth and has to be created in a lab. We have created several elements this way.

There is therefore recent precedent for expanding the periodic table. Scientists are actively working on expanding it further, but it is difficult work. These super-heavy elements are very unstable, and creating them requires a lot of time, energy, and expensive equipment. On top of that, the process is fundamentally random, so each try has only a small chance of success.

New elements are unlikely. We've already filled the periodic table for everything with 118 protons and below. As far as we can tell all the heavy elements are crazy unstable so its unlikely you could craft anything useful out of them. We haven't made anything over 100 that has a half life over a year so whatever you create will be extremely radioactive and change its properties very quickly

That said, new compounds/alloys/chemicals are found/created/designed fairly regularly. Alloys of steel with various quantities of nickel, chromium, molybdenum, and other metals are created all the time with slight to significant changes in the properties either making it harder or more flexible or more durable or better tensile strength or more corrosion resistance

There are a ton of different ways to create crystal structures out of atoms, we haven't created anywhere near most of them yet so there are still some oddballs out there with fun properties

The periodic table is not complete, it is just the elements we have found, or made. There is nothing preventing us from adding another row to the table if we make more elements. In fact we have done this twice already which is why there is the strange insert into the table.

The problem is that elements with higher atomic numbers then uranium is not found in nature because they are highly radioactive. Any elements formed in supernova events will have deteriorated by the time it formed into planets. This is as I recall because the optimal number of gluons for the mixture of protons and neutrons is not a whole number and therefore never achievable.

But if you pay attention this does not mean that there is a second area of stable elements further down in the periodic table of elements. In fact there might be stable isotopes of some of the last elements we have made. We have not found any of them on Earth, or by looking elsewhere in the universe. However this does not mean such an element does not exist. It is possible that in the optimal conditions in a supernova some of these elements might be formed. And these might then become part of a globular cluster and form ore vains in planets in these. It is highly unlikely but still theoretically possible.

What is more likely is that we might find planets rich in elements that we desire. It can be as simple as iron, coal, silica or aluminium, but might also be nickel, lithium or chrome. In literature it is not important exactly which element it is so they just call in unobtainium partly as a placeholder and partly as an in-joke.

The periodic table is open at the bottom.

We have found the first 118 ones and filled up the top 7 row in the periodic table.

People are actively working on getting started on the 8th row and beyond. The problem is that all these elements are unstable. And the last few ones that we "discovered" were already so unstable that they only existed for a tiny moment before decaying.

It gets harder and harder to make them as we go along and what you get out of exists for shorter and shorter amounts of time.

There is expected to be a region deeper down in the periodic table where elements become more stable again. But that is only relative to all the other stuff around it.

Don't expect anyone to come up with a magic metal tomorrow but don't be surprised if at some point in the near future you read an article about a new element created in a lab.

There is also the possibility of making stuff out of things other than combinations of protons, neutrons and electrons as our elements are.

Don't expect anything there that will freely exist in nature and that you can touch with your won hands, but the possibility for stuff to exist however briefly outside the normal domain of chemistry is there.

Most sci-fi stories either invoke magic or wave their hands or don't discuss at all how their wonder materials allows for timetravel, ftl, anti-gravity or ist just incredibly hard and unbreakable.

That is not something we should expect from any new elements or undiscovered particles or matter.

Is there anywhere I read about that "island of stability" in somewhere layman terms? That sounds interesting.

https://the-gist.org/2020/07/new-elements-island-of-stability/

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🎶 These are the only ones of which the news has come to Harvard. And there may be many others but they haven't been discovered🎶

Most of the breakthroughs we have toward unobtanium like properties has arisen from research into alloys (combining elements to make unique metals), or ordinary elements in completely radical environments. Examples are with batteries and ability to hold more charge and charge quicker (combining known elements in new ways) and superconductors (known elements and compounds at extremely cold temperatures).

You don't have to create new atomic elements to make significant breakthroughs in materials. You can do a lot by working with what is already known in new and imaginative ways.

To the best of our knowledge, uranium has the highest atomic number of naturally occurring elements (Z=92). Anything above that (93 - 118) was synthesised in a particle accelerator. There's no reason why we can't continue to do this with higher and higher atomic numbers but most of the nuclei are so unstable that they only exist for a fraction of a second before disintegrating, so they have no practical uses. There is a hypothesised "island of stability" where some semi-stable nuclei could exist with longer half-lives but again it's unlikely that anything will exist long enough to be useful.

So we MIGHT find some new elements out in space but they'd almost certainly be synthesised by an alien race and be extremely short-lived.

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The question was specifically about elements of the periodic table. But you are completely right that the concept of unobtainium comes from the research into alloys. Things like magnesium aluminium creating light but very strong metals, then titanium alloys with even better properties and so on. A lot of this research have faded from the spotlight after plastics took over most of the uses, for example in fiberglass. Currently things like kevlar and carbon fiber have taken over the spotlight from metal alloys so things like unobtainium is hard to imagine for most people.

Once you get over atomic numbers of 100 the elements are unstable and rapidly decay into lighter element, it isn't likely that there will be any new element on a new planet, there will be unusual combinations of elements to create new metals etc. form from existing elements which are rare on Earth, but that is about it.

Eh, there's still a lot of interesting things going on in batteries. The new frontier is nano-materials, though. This is where shit can get wild and into real "unobtanium" type properties. Self repairing materials. Materials that can change properties depending on conditions. Molecular robots. A lot of work is being done around carbon, but there is still a wide open range of possibilities.

Oop. And ceramics. That's been a lot of the last 50 years. I keep saying batteries, but there's an increasing amount of money going into conductors and energy storage. But, ceramics have been hot for awhile.