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Question

What do you mean by valency?


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Solution

Valency:

  • Valency of an element is the number of electrons lost or gained or shared with other atoms in the formation of compounds.
  • The electrons that are present in the outermost shell are known as valence electrons.
  • The valency of representative elements is equal to the number of electrons in the outermost shell for groups 1 and 2, for groups 13 and 14 subtract 10 from group number and 8 minus the number of electrons in the outer most shell for groups 15- 18.
  • Inert gases like He,Ne,Ar,Kr,Xe, etc ( which are belongs to 18th group elements ) normally do not enter into chemical bonding and hence their valency is zero.

Example 1:

  • Consider the Lithium Li atom having an atomic number 3 and it belongs to I A group element
  • The electronic configuration of Lithium Li is1s22s1.
  • The number of valence electrons in lithium is 1. Thus, it must lose one to attain stability ( To get more stable electronic configuration of inert gas). Therefore, the valency of Lithium Li is 1.

Example 2:

  • Consider the Nitrogen N atom having an atomic number 7 and it belongs to 15 A group element
  • The electronic configuration of Nitrogen N is1s22s22p3.
  • The valency of Nitrogen N is 3 as it gains 3 electrons to get more stable inert gas Neon (Ne) configuration.

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