Question

20. Helium atom has 2 electrons in it's valence shell but its valency is not 2 Explain​

Answer 1

Answer:

Valency means the tendency of an element to donate or take electrons. But in the case of helium, which is inhert, it's valency is 0 as it's shell is completely filled which means that it will neither take nor lose electrons

Answer 2

Answer:

because its outer most orbit is completed as we know no. of gaining or losing electron but noble gases have zero valancy as there outermost orbit is completed