VALENCY OF ELEMENTS

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 VALENCY

Definition:- It is defined as the number of electrons lost, gained or shared by one atom of an element in order to attain the stable configuration of inert gas element. 

Ex :- In sodium chloride, sodium losses one electron to attain the stable configuration. Chlorine gains one electron and attains the stable configuration. 

Therefore in NaCl, the valency of Na is +1 and Cl is -1 . 

Sodium            Chlorine

Symbol -                Na                                Cl

Atomic number-    11                                17

Electronic

Configuration -     2,8,1                         2,8,7  

Na+ (2, 8)               Cl- (2, 8,8) 

 VARIABLE VALENCY 

There are some elements which show more than one valency. Elements showing variable valency are usually found to exhibit two valencies. 

(i) Lower valency      and     (ii) Higher valency

  • The lower valency is called the 'Ous' valency. That means we represent the lower valency by adding suffix  'Ous'. 
  • The higher valency is called 'ic'. That means to represent the higher valency the suffix 'ic' is attached.  
Ex :- i) Copper [Cuprous(Cu+), Cupric (Cu++ or Cu2+) ]
ii) Iron [Ferrous (Fe++), Ferric (Fe+++) ]
iii) Mercury [ Mercurous (Hg+), Mercuric (Hg++) ]
iv) Tin [Stannous (Sn++), Stannic (Sn++++ or Sn4+) ]
v) Lead  [Plumbous (Pb++), Plumbic (Pb++++) ]
vi) Antimony [Stibous (Sb+++), Stibic (Sb+++++) ]
vii) Gold [ Aurous (Au+), Auric (Au+++) ]
viii) Arsenic [ Arsenous (As+++), Arsenic (As+++++) ]




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