How to find the number of valence electrons with the help of quantum numbers? [closed]








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I'm bit confused on how to find the number of valence electrons. For example, Boron ($\ce{B) has the electronic configuration as: $\mathrm{1s^2 2s^2 2p^1}$. So what would be its number of valence electrons : 1 or 3. According to me the answer should the 1 as the last orbital ($\mathrm{p}$ orbital) has 1 electron. Am I wrong? Please guide me if I am wrong.




Any electrons present in the electron configuration of the element in question, but not present in the nearest noble gas with an atomic number below that of the element, is a valence electron.


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