Question

Identify the element which shows variable valency ?

• A. Helium
• B. Sodium
• C. Magnesium
• D. Iron

Answer 1

Answer:

D. Iron

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.