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Identify the element which shows variable valency ?

AHelium

BSodium

CMagnesium

DIron

Answer:

D. Iron

Read Explanation:

The valency of an element is the number of electrons it gains or loses or shares to attain the noble gas configuration. d block elements always exhibit variable valancies and different oxidation states.

  • Iron is a d-block element, so it shows variable oxidation states.
  • The atomic number of iron is - 26



  • Iron exhibits 2 valence states of +2 and +3.
  • When iron loses the 2 4s electrons, it attains a valency of +2.
  • Sometimes, iron will also lose one of the paired electrons from 3d orbital, leaving the entire 3d orbital filled with unpaired electrons (which provides a more stable configuration). In this case, its valency will be +3.
  • After losing one electron from the d subshell it will become a half-filled subshell. This 3d⁵ is a stable electronic configuration.
  • Hence the element of iron shows 2 and 3 valencies. These valencies are called iron variable valencies.

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