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Structure of the Atom — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceStructure of the Atom2 Marks
Question
Why do helium, neon, and argon have zero valencies?
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Answer

Valency,the combining capacity of an element is equal to the no. of electrons needed to be removed from the outer most shell of the atom of the element, to have a complete ‘octet’.
He(2)
Electronic configuration : 2
Complete octet.
Ne(10)
Electronic configuration :2, 8
Complete octet.
Ar(18)
Electronic configuration : 2, 8, 8
Complete octet.
Since the octet is complete so there is no need to remove any electron. So the valency is 0.

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