How come there are no gaps in the table? If there are 118 elements currently, and the next element to be discovered/created has an atomic number of 120, would there just be a gap at 119th position?
How come we managed to find/create every element without any gaps in the periodic table?
In: 104
The atomic numbers are just the quantity of protons which are obviously just positive integers (whole numbers, 1, 2,3, you can’t get 1.255 protons)
In fact your point is why the Periodic Table was so significant because before we arranged elements like this we *were* missing elements and didn’t know it! For example, the 1st periodic table didn’t have the noble gasses at all (we didn’t know they existed).
But some people sat down and say, Wait? Why are missing elements? And they went out and discovered them!
It’s totally possible we’ll find gaps as we discover new elements, but that doesn’t mean they don’t exist, we’ll leave a spot for them as we know they *must* exist, we just haven’t discovered them yet!
EDIT – as u/ComradeMicha has pointed out the largest elements are highly unstable and not found in nature, we can only create them for fractions of a moment within laboratory settings before they decay (break apart). There is a idea of something called “The Island of Stability” where we might discover (read: create in a lab) super heavy elements that *are* stable without decaying, but we haven’t discovered any yet.
There would just be a gap, and in some outdated periodic tables, there are gaps where we discovered elements out of order. We’ve discovered every element up to 118 because radioactive elements *generally* become less stable the heavier they are, so we’re more likely to discover them in order from lightest to heaviest.
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The numbers in the periodic table are based on the number of protons that a particular atom has. Since protons are (for the sake of this ELI5) an indivisible unit, the periodic table can’t have any gaps – you can’t have half a proton in the nucleus of an atom.
We arrange them based on proton number because _that_ is what determines the nature of the atom itself. Atoms routinely gain or lose electrons, and while increased/decreased neutrons create isotopes that have _slightly_ different properties it is the proton that determines how the atom will behave.
This knowledge is what allowed us to construct the table, even when we had yet to discover particular atoms – we _knew_ they would be there because we can extrapolate the number of protons in the gap. This was the case for Technetium, which was only discovered in 1937, while the table itself dates back to 1869.
Each atom contains a nucleus, which consists of a number of protons and neutrons. These protons and neutrons attract and repel each other through a very complicated (and still not entirely understood) set of interactions involving three forces: the strong nuclear force, the weak nuclear force, and the electromagnetic force. It turns out that many different arrangements of protons and neutrons can form a stable nucleus, while others very quickly break apart (“decay”), and others last for a long time before decaying. The atomic number is simply the number of protons in the nucleus, and it turns out that for most atomic numbers there is at least one arrangement that is stable or that holds together for a reasonable amount of time before decaying.
Pretty much all of the stable isotopes can be found in nature somewhere (originally they were mostly created by fusion in stars, or in high-energy events such as supernovae) and many of the unstable ones are continuously created during natural decay processes. For example, there are no stable isotopes of uranium, but some of them decay *extremely* slowly, so there is still plenty of uranium around on earth even though it was created billions of years ago. The slow decay of uranium constantly produces various other isotopes, including for example isotopes of radon, none of which are long-lasting. But because it’s being constantly produced, radon gas can build up in caves and basements and cause health problems.
The remaining isotopes, mostly those with very high atomic numbers, have had to be created and detected in labs. The ones with the highest atomic numbers tend to be extremely unstable, so are very difficult to detect before they decay. In principle there might be an element whose isotopes are *so* unstable that it just isn’t feasible to detect them, so there might be a permanent gap, but that hasn’t happened yet.
Originally the periodic table did have gaps, and that’s part of why making it was so important: it told us what we were missing. The number on the periodic table, known as an “atomic number” is how many protons an atom of that element has. So hydrogen is number 1 and has 1 proton, platinum is number 78 and has 78 protons, and so on.
When we initially made the periodic table there were gaps, those gaps told us we were missing something, so we started to look. For example when the periodic table was created in 1869 we had discovered moldybenium, which has 42 protons, and ruthenium, which has 44 protons, but didn’t have something with 43 protons. By putting them on that table we were able to realize this, we were able to notice these gaps and say “well if there are elements with 1 proton, and 2 protons, and 3 protons (all the way up to 42) and ones with 44 protons, and 45 protons, etc., so there must be something with 43 protons that we haven’t found yet.” So we started looking and in 1937 a scientist named Emilio Segre discovered technetium, an element with 43 protons.
That said we don’t necessarily go up by 1 at a time. Not everything on the period table is a naturally occurring element, some of them are synthetic. Uranium, element 92, is the heaviest element that exists in sizable quantities, though it looks like there may be some naturally occurring sources of californium, element 98. Long story short most elements heavier than Uranium were synthesized in a lab. These synthetic elements often go up by 1, but they don’t necessarily go up by 1, which can leave gaps. For example Meitnerium (109), was discovered two years before Hassium (108). The heaviest element we have, Oganesson (118), was discovered before Nihonium (113), Moscovium (115), and Tennessine (117). If the next element we synthesize was to have 120 protons there would just be a gap at 119 until we got synthesized something with 119 protons.
>How come there are no gaps in the table?
Because we filled them. The table used to have gaps, then we discovered those elements.
>If there are 118 elements currently, and the next element to be discovered/created has an atomic number of 120, would there just be a gap at 119th position?
Yes
>How come we managed to find/create every element without any gaps in the periodic table?
We didn’t, as said, the first periodic table did have gaps and then we filled them. Even in modern times we didn’t synthesize new elements sequentially:
* 103 came before 102
* 109 came before 108
* The last few came in the following order: 112, 114, 116, 118, 113, 115, and then 117.
Iirc it basically comes down to we can do the math for these elements you speak of and they can’t exist on earth but we haven’t traveled through out space and time yet and that’s what the whole point of chemistry and physics when it gets to a certain degree
Edit : but they may exist elsewhere
If you are really interesed in chemistry or elements, the youtube channel periodic videos cover all of them and even the history and evolution of the periodic table.
[WE <3 the periodic table](https://www.youtube.com/watch?v=Zgge1O9wdPY)
Technically, the atomic numbers are NOT continuous–they are very much discrete (there is no element 56.7), and based upon the number of protons in the atom. We can always add a proton to a nucleus and increase the atomic number by 1–which is why you say they are “continuous”. The resulting element may not be stable and may very quickly decay.
Interestingly enough, the early periodic table was originally developed by Mendelev in 1869–preceeding the discovery of the electron (1897), the proton (1917), and neutron (1932). The atoms were arranged by atomic weight and not by atomic number. Mendelev (and others) noticed that there was a periodicity of the behavior of the then 64 known elements. He noticed that there were “holes” in his table, and (correctly) predicted new elements and their general properties that filled the holes.
Overtime chemist and scientists discovered new elements and placed them in the correct positions. The last sub-uranium element to be discovered was Promethium (61) in 1945. The lowest atomic number element yet to be discovered in the twentieth century was Technitium (43) discovered in 1937.
Several of the last found sub-uranium elements do not exist in the Earth’s crust in any non-negligible quantity. They were generally found in uranium ore and were transitory steps in the decay chain of uranium.
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