Valency

The capacity of an atom to give , accept or share electrons to achieve there octet state.

OR

The number of electrons gain, lost, or share by the atom of elements so as to complete is octet (or duplet in case elements having only K shell) is called valency of elements.

  • Here comes the concept of valency.
  • Valency is combining capacity of elements. ( that is how much atom bonds with another atom.
  • There for capacity of atom to give, accept or share electrons to achieve stable is called valency.
  • 1st. Shell have the capacity maximum two electrons called duplet.
  • Remaining shell have the capacity eight electrons called Octet.
  • For example He  and Ar. Are stable elements.

Distribution of electrons in shell:

2n2    n= designation.  K shell (n=1) , L shell (n=2) , M shell (n=3) , N shell (n=4) ,

K shell: 2(1) 2 = 2

L shell:2(2) 2 = 2×4= 8

M shell:2(3) 2 = 2×9= 18

N shell:2(4) 2 = 2×16=32

  • The third M shell can be hold 8, or 18 electrons but the total capacity of third shell is 18.

 

  • The outer most of the orbit or shell of elements electron called valence electrons. Or valence shell.
  • The valence electrons present in outer most of the orbit or shell.
  • For example outermost shell of hydrogen one electrons present so the valency of hydrogen is one. So it tends to gain one electrons, or share one electrons for to be stable.
  • Lithium electronic configuration is 2,1 so outermost shell have one electrons so the valency of Li is one, it tend to lose one electrons and become stable.
  • Magnesium electronic configuration is 2,8, 2 So outermost shell have 2 electrons that Mg is unstable, for the stability Mg lose their two electrons and become stable.
  • We can get valency of elements or atom by following simple methods.

1) The valency of an elements= the number of valence electrons ( outermost shell electrons)

(when the number of valence electrons {outermost shell electrons}     are 1-4 , that is those elements outermost shell have 1,2 3,4 electrons the valency are same number of outermost shell electrons present in it.)

2) The valency of an elements = 8  – number of valence electrons ( outermost shell electrons)

  • For example Helium have two electrons their Outermost shell so Helium valency is 2 .
  • Oxygen electronic configuration O-2,6 so by second method

The valency of an elements = 8  – number of valence electrons

=  8  – 6

= 2

Therefore, the valency of oxygen is two (2).

  • Chlorine electronic configuration Cl- 2,8,7 by second method,

The valency of an elements = 8  – number of valence electrons

=  8  – 7

= 1

Therefore, the valency of chlorine is one (1).

  • Carbon electronic configuration C- 2,4 by first method,

The valency of an elements = the number of valence electrons

4     =    4

Therefore, the valency of carbon is four (4).

Elements

Symbol Valency

Hydrogen

H

1

Fluorine F

1

Chlorine

Cl 1
Bromine Br

1

Iodine

I 1
Oxygen O

2

Magnesium

Mg 2
Nitrogen N

3

Carbon

C

4


Question Answer

1) What is valency?

Answer: The capacity of an atom to give , accept or share electrons to achieve there octet state

2) What is valence electrons?

Answer: The outer most of the orbit or shell of elements electron called valence electrons.

3) How to get valency of oxygen?

Answer:  Oxygen electronic configuration O-2,6  so by simply method

The valency of an elements = 8  – number of valence electrons

=  8  – 6

= 2

Therefore, the valency of oxygen is two (2).

4) How to get valency of oxygen?

Answer: Nitrogen electronic configuration N-2,5  so by simply method

The valency of an elements = 8  – number of valence electrons

=  8  – 5

= 3

Therefore, the valency of oxygen is three (3).

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