Question

how to calculate the valency of iron?

Answer 1

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.

Answer 2

Answer:

+2 or +3

Step-by-step explanation:

Valency : It is defined as the number of electrons should  gain or loses when an element to complete filled its outer shell .In other words , we can say it is defined as charge that carry by an ion which tell us that how much electrons gain or lose by an element to make that ion.

If valency is negative then an element gain electrons to completely filled its electronic configuration.When valency of an elements is positive then an element lose electrons for filling of outer shell.

Atomic number of iron is 26

Then its electronic configuration is

$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6$

Then iron exhibit valency +2 and +3

When iron exhibit +2 valency then iron loses 2 electrons to complete its outer shell

When iron exhibit +3 valency then iron loses 3 electrons for completely filling its outer shell