Explain the following
(a) Valency

Explanation

Valancy : Valency is the combining capacity. It is the number of atom of hydrogen or chlorineor any monovalent atom, with which one atom of the element combines.
Generally all the elements in a group show the same valency. In case of s-block elements valency = group number.
In case of p - block of elements,
Valency = group number, or (8 -group no.)
Variation of valency w.r.t hydrogen, in a period : In representative elements, the valency increase from 1 to 4 and then decrease to 1 from left to right.
Ex : Valency of 3rd period of elements:
`{:("name of element",Na,Mg,Al,Si,P,S,Cl),("Valency w.r.t.H",1(NaH),2(MgH_(2)),3(AlH_(3)),4(SiH_4),5(PH_3),6(H_2S),7(HCl)):}`.