define the valency of iron
Answers
The words valence and valency have two related meanings in chemistry.
Valence describes how easily an atom or radical can combine with other chemical species. This is determined based on the number of electrons that would be added, lost, or shared if it reacts with other atoms.
Valence is denoted using a positive or negative integer used to represent this binding capacity.
Valency is the combining capacity of the atom of an element. It is equal to the number of electrons an atom can donate or accept or share.
Iron shows more than one valency which is also known as variable valency.
Iron shows two valencies:
Fe2+,ferrous.. And Fe3+ ferric
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Answer:
The valency of an element is the number of electrons it gains or loses or shares to attain the noble gas configuration. In other words, how any electrons should an element lose or gain or share to have a completely filled outer electronic shell.
Iron (Fe) has an atomic number of 26, i.e. has 26 electrons.
Its electronic configuration is given as: 
The energy of 4s and 3d orbital is similar (4s has slightly higher energy). Also note that the 3d orbital has 1 electron pair, rest of the electrons are unpaired.
Now, 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.
Hope this helps you.