The guy who made up the periodic table (Mendeleev) worked it out using clever rules which allowed him to categorise the elements and predict even the ones that hadn’t been discovered yet. There have also been some new elements discovered recently – but they exist for very very short periods of time.
I think it’s all down to stability…
So what characterises an element is its atmoic number, how many protons there are in the nucleas.
The heavy elements that have been more recently discovered have only been discovered more recently due to better and newer technology and analsysing equipment. The heavier elements tend to be more unstable and even radioactive, which means they decompose into two smaller more stable elecments….
I think they may be a few more elements out thier, but they are probaly unstable to would have to be observed under certain conditions..
Hello butters! This is a really great question. As Amy and Julia have said, the reason is primarily stability. As we go up in atomic number we are increasing the numbers of neutron and protons in the nucleus of the atom. However, as you add more and more and more the nucleus becomes unstable. You are packing in a lot of protons for example, which all have the same electric charge.
Typically the strong nuclear force can overcome this electromagnetic repulsion. The strong force is one of the four fundamental forces of nature (like gravity, the electromagnetic force, and the weak force) and acts to hold the neutron and protons together in such a tightly packed space as the nucleus. However the strong force only operates on really tiny distances. So a large nucleus becomes unstable – the strong force doesn’t operate on large enough spatial scales to hold it together! As we discover more atoms with higher atomic number we discover they have shorter and shorter lifetimes for this very reason. They are unstable. So we can’t have atoms of unlimited size – good thing too because we probably wouldn’t have life if we could!