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Discuss about place of He and H. |
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Answer» SOLUTION :Two elements like hydrogen and helium are observed as an exception . Place of hydrogen in periodic table : Hydrogen contain le in ls orbital so it must be SITUATED in group-1. Hydrogen accept `1 e^(-)`and from stable structure like helium. So, it must be situated in group-17 But there is same difference observed between hydrogen and ist group and hydrogen and `17^(th)`group so hydrogen atom is situated in separately in periodic table. Place of helium in periodic table . Helium element having `1 ^(st)`electron configuration so it must be present in s-block. But its positioning in the p-block along with other group 18 elements is Justified. Because it has a completely filled valence SHELL `(1 s^(2))` and as a result, exhibits properties characteristic of other noble GASES. |
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