Question

Helium atom has 2 electrons in the valence shell but its valency is not 2.Explain.(1)​

Answer 1

Answer:

Helium atom with electronic configuration 1s2 has two valence electrons but since it is a noble gas, it does not form a chemical bond, its duplet is complete. Therefore, valency is zero.

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Answer 2

Answer:

because according to octet rule first orbital should have two electrons, and helium has it all, so helium is a stable atom and doesn't share electrons, so it's valency is 0.