Hi, the wikipedia article on fermium states that it is the last

[Jarwulf]

Hi, the wikipedia article on fermium states that it is the last element that can be synthesized by neutron bombardment but decides not to explain why. Can anybody give a layman's explanation? Thanks.

 

[Drakkith]

Elements heavier than Uranium and Plutonium are created when neutrons are absorbed into the nucleus and then Beta Decay into a proton. This creates a new element since the number of protons differentiate the different elements. Past fermium, I'm guessing that the nucleus will no longer absorb a neutron and then beta decay. It most likely will fission or simply eject other particles as soon as the neutron is absorbed.

 

[Jarwulf]

Elements heavier than Uranium and Plutonium are created when neutrons are absorbed into the nucleus and then Beta Decay into a proton. This creates a new element since the number of protons differentiate the different elements. Past fermium, I'm guessing that the nucleus will no longer absorb a neutron and then beta decay. It most likely will fission or simply eject other particles as soon as the neutron is absorbed.

Yeah but what is the reason behind that? And why would you be able to do it instead with something like an alpha particle?

 

[Drakkith]

Yeah but what is the reason behind that? And why would you be able to do it instead with something like an alpha particle?

absorption of an alpha particle immediately changes the atom to another element since you are adding 2 protons.

As to the why, I can't tell you. I'm not an expert on nuclear physics.

 

[Bill_K]

Primarily because of the short half-lives. You need a target that will sit still long enough. And neutron bombardment followed by beta decay only takes you one step up, Z -> Z + 1. Using alpha particles instead will take you two steps, but more realistically it's better to use heavy ions. To make Nobelium they used ¹³C ions. Rutherfordium it was ²²Ne, Seaborgium it was ¹⁸O, and so on. The highest element named so far, Copernicium (at no = 112), was found using ⁷⁰Zn on ²⁰⁸Pb.