How to calculate the position of an element from its atomic number? [closed]








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How to calculate the place of of a element if know their atomic number in a periodic table?




You will not fail following the numbers of periodicity from one electron in the outer electronic shell to the completely filled shells. Shells are filled


* in the first shell with **2** electrons ($\ce{\_2He}$),
* in the second shell with **8** more electrons ($\ce{\_10Ne}$)
* in the third shell with again **8** more electrons ($\ce{\_18Ar}$)
* in the fourth shell with **18** more electrons ($\ce{\_36Kr}$)
* in the fifth shell with again **18** more electrons ($\ce{\_54Xe}$)
* in the sixth shell with **32** more electrons ($\ce{\_86Rn}$)
* in the seventh shell with - you guess - again **32** electrons.


The positions of elements were arranged empirical by their chemical properties by [Mendeleev](https://en.wikipedia.org/wiki/Dmitri_Mendeleev) in 1865. Years later it became clear that atoms consist of electrons, arranged around the nucleus and the mentioned above electron configurations are inert or [Noble gases](https://en.wikipedia.org/wiki/Noble_gas).


Unfortunately physics claims shells to have [$2n^2$](https://en.wikipedia.org/wiki/Electron_configuration#Shells_and_subshells) electrons (where $n$ is the number of the shell). Which brings you to the point to learn about [Aufbau principle and Madelung rule](https://en.wikipedia.org/wiki/Electron_configuration#Atoms:_Aufbau_principle_and_Madelung_rule).


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