Question

Helium has two valence electrons, but its valency is not 2. Explain.​

Answer 1

Because it's duplet is complete, it can neither gain electrons nor lose electrons.

Answer 2

Answer:

It is because for the first shell maximum limit is 2.

By having 2 valence electrons it has completed its duplet.

By completing its duplet, its has become stable and cannot gain or lose any electrons which makes its valency two and not zero.