a few questions about elements

[General_Thral]

Been watching some videos on youtube about elements and it was very interesting but have been pondering on a few things:

We seem to be finding or making predictions about new elements , but how many are there exactly?

How come the elements we are finding now we need particle accelerators in order to be created , how come these are not found naturally occurring around us?

And when we do find them , do any of these elements have any useful characteristics , i mean im always watching the discovery channel about ex area 51 employees reverse engineering alien craft that somehow have this unknown element that give them there faster than light propulsion but are undiscovered elements capable of properties such as this? Does discovering new elements lead to new technologies being researched?

[Magicman2051]

There isn't an exact figure, theoretically infinite, practically speaking however the Periodic Table covers it.

Elements like hydrogen or lithium are reasonably common because they are simple, the more complex elements like gold (for example) are usually only created during the death throes of a star and are thus less abundant. That said, we're not actually finding new elements in particle accelerators, we're finding the building blocks of protons, neutrons etc.

Does discovering new elements lead to new technologies being researched?

Simply put yes, you just need to look at history to see that.

[Sphere]

We seem to be finding or making predictions about new elements , but how many are there exactly?

How come the elements we are finding now we need particle accelerators in order to be created , how come these are not found naturally occurring around us?

There are two main forces working opposite eachother in the nucleus; 1.)the Strong nuclear force which attracts protons to neutrons and to other protons. This force holds the nucleus together. 2.) the electromagnetic force, which causes the positively charged protons to repel each other (neutrons are neutrally charged so they have no electromagnetic effect)

The Strong force is, well, very strong. But only over very, very short distances compared to the electromagnetic force. Once you start getting a large nucleus the protons & neutrons become farther and farther apart with the effect that the average force binding a proton in the nucleus starts to reduce...



At around the size of Uranium the strong nuclear binding force on the protons is on par with their electromagnetic repulsion of the protons. So smaller atoms than Uranium stick together (non-radioactive) and bigger atoms than than uranium cannot stay together (radioactive). You can also get this radioactivity by shooting in extra neutrons into a normally non-radioactive element and spreading out the protons.

[Jack04]

Been watching some videos on youtube about elements and it was very interesting but have been pondering on a few things:

We seem to be finding or making predictions about new elements , but how many are there exactly?

How come the elements we are finding now we need particle accelerators in order to be created , how come these are not found naturally occurring around us?

And when we do find them , do any of these elements have any useful characteristics , i mean im always watching the discovery channel about ex area 51 employees reverse engineering alien craft that somehow have this unknown element that give them there faster than light propulsion but are undiscovered elements capable of properties such as this? Does discovering new elements lead to new technologies being researched?

Unless we find the island of stability (http://en.wikipedia.org/wiki/Island_of_stability) you're not likely to run into anything higher than uranium unless you're working specifically with transuranium isotopes, and even then, there aren't a huge number that can be produced.

The trouble working with elements beyond uranium is that the neutron/proton balance becomes increasingly neutron heavy. This means that simply adding a couple of stable isotopes (tin is particularly popular) together wont cut it any more, because that'd leave you with an N=Z, high mass isotope, which at the masses concerned is likely to be beyond the proton drip-line and will therefore fall apart almost instantly.

The current technique effectively just uses a high energy radioactive isotope beam and slams it into a target, before measuring the resultant output's mass and charge (which is effectively all you need to know to identify an isotope). Interestingly, this technique was thought to be almost impossible, so only one lab (in Russia) ever bothered with it. Which means that these elements have not all been verified by other experiments, which are rushing to catch up.

Essentially, the high Z (high proton number) elements may exist naturally, but they will be in such minute abundances that they will be almost impossible to find, and that's if they exist in a stable enough form to survive.

... and new elements would just be denser. They wouldn't have any special properties beyond those found already in the periodic table.

The Segrey chart shows you the relevant information w.r.t your first question, as you can see, as mass increases, stable isotopes move further into the neutron rich region. Which is a problem for creating heavier elements, as I mentioned earlier: