plutoniumm

[bednobs]

as iunderstand it, plutonium is a by product of nuclear fission and is also an element. So before the first nuclear fission, was there a space in the periodic table for it, or did they just have to slot it in when it happened?

[Old_Geezer]

The periodic table is a man made construct, but it comes firly naturally given that the characteristics follow rules regarding electrons in "orbit" around each nucleus. So yes there would have ben a slot someone could have predicted plutonium would fill.

[Old_Geezer]

Seems to be typo day today.

[Tim123]

Plutonium is a by product of fission reactors, but is actually produced as a result of nuclear fusion. It exists in nature in trace quantities. The periodic table is a table of elements arranged according to the number of protons in the atomic nucleus. There was always a position for an element with 94 protons, even before it was isolated and named.

[R1Geezer]

Indeed, most of the periodic table was defined before the actual elements were tracked down. There were empty slots were it was predicted they would fit but it took time to find/identify them all.

[jake-the-peg]

Er well none of the plutonium on Earth was produced from what we normally describe as nuclear fusion.

Nuclear fusion happens when two fast moving nucleii collide with enough force to overcome the electric repulsion of their charges and the strong nuclear force hold them together.

Plutonium comes from the Uranium 238 capturing a slow moving neutron in a nuclear reactor and then decaying to produce Plutonium.

So Yes in a very vague sense it's fusion but that's not what we normally use the word fusion to describe.

When neutrons under go beta decay they emit an electron and become protons that's how Uranium becomes plutonium.

Now back to the original question:

People didn't understand the relationship between the elements at first but they noticed that many had very similar properties. Many people had a go at arranging them but eventually a Russian called Mendelev hit upon the predecessor to the periodic table.

It had many gaps in it where elements were assumed to exist and over the years people slowly found the new ones and filled in the gaps.

Have a google for him, It's a fascinating story

[bednobs]

hi, thanks for all this. How does anyone know when the periodic table is "finished"? There may be many more undiscovered elements that have 235electrons or 1321 electrons

[bednobs]

ps if i could mark you ALL as the best answer i would, but seeing as marking the best answer dosen't actually DO anything, and you all can't see it it dosen't matter anyway!

[jake-the-peg]

That's a really good question!

As atomic nucleii get bigger the electric repulsion between them gets stronger and the nuclear force need more and more neutrons to hold it together. Eventually it just can't which is why all the heaviest elements are radioactive.

The very heaviest have tiny half-lives vanishing almost as soon as they are created - and they have to be created in complex experiments.

Some people have speculated that there might be "islands of stability" further up but it's a bit of a long shot.

[Old_Geezer]

I don't think there is a finish to it as such, you can go on adding heavier and heavier elements 'until the cows come home'. But the thing is that most of these elements would be very unstable so even if you could force them into creation they would break up almost immediately.

I recall once many years ago (I think it was in New Scientist) that it was proposed there may be possible "islands" in the table where some heavy elements may prove stable, but I don't know if that was ever confirmed or disproved.

[Old_Geezer]

Oh I should have read Jake's answer first. Typical me.

[bednobs]

thank you OG