Question

why helium have valency = 0

Answer 1

$\large \tt AHOY!! \:$

first of all, what is valency?

valency is the combining capacity of an atom.

we know that there are 4 shells in an atom, K,L,M and N.

K shell can accommodate maximum 2 electrons and L,M and N can accommodate maximum 8 electrons.

the atomic number of helium is 2.

so the outermost shell of helium will be K and K can have maximum number of electrons 2.

hence, there will be no need of gaining or losing electrons.

that's why helium have valency = 0

$\large \tt HOPE \: THIS \: HELPS!!$