Question

What is the valency of helium and phosphorus? And why?

Answer 1

helium has a valency 2 because
Valency,, the combining capacity of an element, is equal to the number of electrons needed, or required to be removed from the outermost shell of the atom of that element, to have a complete 'octet'. The helium atom has only the 1s orbital in its only shell, and it is completely filled with 2 electrons.
and phosphorus has its valency is 3

Likewise, one atom of phosphorus combines with three atoms of hydrogen to form the normal hydride phosphene, PH3. Therefore, the valency of phosphorus is 3 only....
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