Okay, so I understand that the number of protons in an atom defines the element. But why are there only 118 of them? Can’t we keep on adding protons to an atom to create new elements?

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EDIT: Thanks for all the responses!

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28 Answers

Anonymous 0 Comments

The answer is yes and no. Many of the “transuranium” elements are basically more or less artificiality made in nuclear laboratories and only last for an incredibly small amount of time and then decay. It’s not like we are building the elements and then mass producing them and building stuff out of them. They exist maybe theoretically more than anything, but they have been made and have been named.

This wikipedia article goes into a lot of detail about them.

https://en.wikipedia.org/wiki/Transuranium_element

Anonymous 0 Comments

Sure you can, but the further you go the more unstable these elements become. Some of the ones on the currently described top end are purely man-made, only existing for a tiny duration of time in a lab before they decay.

E: there are [some exceptions](https://www.reddit.com/r/explainlikeimfive/comments/11187pi/eli5_okay_so_i_understand_that_the_number_of/j8f456t/)

Anonymous 0 Comments

Sure you can, but the further you go the more unstable these elements become. Some of the ones on the currently described top end are purely man-made, only existing for a tiny duration of time in a lab before they decay.

E: there are [some exceptions](https://www.reddit.com/r/explainlikeimfive/comments/11187pi/eli5_okay_so_i_understand_that_the_number_of/j8f456t/)

Anonymous 0 Comments

We can but those elements would be unstable and fall apart almost immediately. Bismuth (83) is the last truly stable element (more precisely, the last element with at least one truly stable isotope). The heavier you go after that, the faster your elements fall apart on their own, i.e. go through nuclear (radioactive) decay.

Edit: actually lead (82) is the last stable element, bismuth just has a really, really long half-life.

Anonymous 0 Comments

The answer is yes and no. Many of the “transuranium” elements are basically more or less artificiality made in nuclear laboratories and only last for an incredibly small amount of time and then decay. It’s not like we are building the elements and then mass producing them and building stuff out of them. They exist maybe theoretically more than anything, but they have been made and have been named.

This wikipedia article goes into a lot of detail about them.

https://en.wikipedia.org/wiki/Transuranium_element

Anonymous 0 Comments

There is not just 118 of them. We have just been able to make and measure 118 of them, and it so happens to neatly fill the rows of the periodic table of elements. We have found some evedince that there is elements beyond the 118 we currently know about but these are extremely unstable and we have therefore been unable to do any measurements of their properties.

Anonymous 0 Comments

There is not just 118 of them. We have just been able to make and measure 118 of them, and it so happens to neatly fill the rows of the periodic table of elements. We have found some evedince that there is elements beyond the 118 we currently know about but these are extremely unstable and we have therefore been unable to do any measurements of their properties.

Anonymous 0 Comments

We can but those elements would be unstable and fall apart almost immediately. Bismuth (83) is the last truly stable element (more precisely, the last element with at least one truly stable isotope). The heavier you go after that, the faster your elements fall apart on their own, i.e. go through nuclear (radioactive) decay.

Edit: actually lead (82) is the last stable element, bismuth just has a really, really long half-life.

Anonymous 0 Comments

The protons and neutrons in the the nucleus of an atom are held together by something that’s kind of like magnetism, called the Strong Nuclear Force. The thing is that in the same way magnets only appear to work within a certain distance, the distance the Strong Nuclear Force works is only about the width of a proton. So while it’s very, very strong, it’s only holding each proton to the ones that are “touching” it. It doesn’t hold the whole nucleus together; it just holds adjacent protons together. And because the range of the Strong Nuclear Force is so short, it doesn’t get any stronger if you add more protons.

Meanwhile, there’s another force called Electromagnetism that creates an effect called Electrostatic Repulsion. Electrostatic Repulsion causes the protons to push away from each other. However, Electrostatic Repulsion isn’t very strong when there are only a few protons. But the more protons you add, Electrostatic Repulsion grows stronger and stronger. At a certain number of protons, Electrostatic Repulsion becomes stronger than the Strong Nuclear Force.

That number of protons is 83. Any atomic nucleus with 83 or more protons is unstable because at that point, Electrostatic Repulsion is working harder to break the nucleus apart than the Strong Nuclear Force can work to keep it together. So Lead, with an atomic number of 82, is the last stable element, while Bismuth, at 83, is the first element that’s unstable. In the case of Bismuth, it would take an unthinkable amount of time for its nucleus to decay, because it’s not *very* unstable. As you go up the periodic table to elements with more and more protons, they (more or less) get more unstable as you go up.

So, TL;DR: At 83 protons in the nucleus, Electrostatic Repulsion gets stronger than the Strong Nuclear Force, so any more protons than that an the nucleus will eventually break apart.

*[Edit]: As some very correct people have pointed out, this explanation is a gross oversimplification that ignores what’s really going on in the underlying particles and forces mentioned here. I was just trying to get as close to an ELI5 answer as I could think of without going into the non-layperson parts of the explanation. But in reality, those “details” really ARE the story, and any simplification of them kind of points you in the wrong direction if you are actually trying to study the real inner workings of the atom.*

Anonymous 0 Comments

The protons and neutrons in the the nucleus of an atom are held together by something that’s kind of like magnetism, called the Strong Nuclear Force. The thing is that in the same way magnets only appear to work within a certain distance, the distance the Strong Nuclear Force works is only about the width of a proton. So while it’s very, very strong, it’s only holding each proton to the ones that are “touching” it. It doesn’t hold the whole nucleus together; it just holds adjacent protons together. And because the range of the Strong Nuclear Force is so short, it doesn’t get any stronger if you add more protons.

Meanwhile, there’s another force called Electromagnetism that creates an effect called Electrostatic Repulsion. Electrostatic Repulsion causes the protons to push away from each other. However, Electrostatic Repulsion isn’t very strong when there are only a few protons. But the more protons you add, Electrostatic Repulsion grows stronger and stronger. At a certain number of protons, Electrostatic Repulsion becomes stronger than the Strong Nuclear Force.

That number of protons is 83. Any atomic nucleus with 83 or more protons is unstable because at that point, Electrostatic Repulsion is working harder to break the nucleus apart than the Strong Nuclear Force can work to keep it together. So Lead, with an atomic number of 82, is the last stable element, while Bismuth, at 83, is the first element that’s unstable. In the case of Bismuth, it would take an unthinkable amount of time for its nucleus to decay, because it’s not *very* unstable. As you go up the periodic table to elements with more and more protons, they (more or less) get more unstable as you go up.

So, TL;DR: At 83 protons in the nucleus, Electrostatic Repulsion gets stronger than the Strong Nuclear Force, so any more protons than that an the nucleus will eventually break apart.

*[Edit]: As some very correct people have pointed out, this explanation is a gross oversimplification that ignores what’s really going on in the underlying particles and forces mentioned here. I was just trying to get as close to an ELI5 answer as I could think of without going into the non-layperson parts of the explanation. But in reality, those “details” really ARE the story, and any simplification of them kind of points you in the wrong direction if you are actually trying to study the real inner workings of the atom.*