FeCl2 Lewis Structure, Characteristics: 9 Facts You Should Know


In this article, we should discuss the FeCl2 lewis structure. Let’s talk about the FeCl2 lewis structure and 9 different characteristics fact.

FeCl2 is often known as ferrous chloride. The ferrous term is coming for Fe in a +2 oxidation state. In the FeCl2 Fe is in a +2 oxidation state. The electronic configuration of Fe(II) is d6. Being a FeCl2 is a coordination compound, Cl is not only a counter ion here it also acts as a ligand. The geometry of the FeCl2 lewis structure is the bent shape, although in the crystal form it adopts an octahedral shape.

As Cl is a soft filed ligand, the electronic paired up is not formed in the d orbital. So, Fe(II) is a d6 high spin system here. Only one subset is paired due to six electrons present in five subsets. FeCl2 lewis structure can be ionized to ferrous and chloride ions.

Some important facts about FeCl2

FeCl2 is a white solid crystalline molecule. It is a paramagnetic solid due to the presence of four unpaired electrons in the d orbital. The color of its tetrahydrate form is greenish, due to its octahedral shape and the Laporte transition occurs. But in anhydrate form is white.

Anhydrates form can be prepared by the reaction of steel waste with hydrochloric acid.

Fe + 2 HCl → FeCl2 + H2

The melting point and boiling points of FeCl2 are950 k and 1296 K respectively.

1.    How to draw FeCl2 lewis structure?

Drawing the FeCl2 lewis structure is not an easy task. As FeCl2 is a coordination compound rather than a covalent molecule. So here d electrons will be involved in the bond formation and it is not easy to manage d electrons for drawing the lewis structure because d electrons follow the 18 electrons rule rather an octet rule. So, we try to draw the FeCl2 lewis structure easily in the following manners.

Step 1– At first, we should count the valence electrons for Fe as well as Cl. The valence electrons of Fe are d electrons and p electrons for Cl atoms and added together. In the FeCl32 lewis structure, the valence electrons for Fe are 6 as it is in a +2 oxidation state, and all the electrons belong from its d orbital only, for three Cl atoms is 7*2 = 14. So, the total valence electrons are 6+14 = 20.

Step 2 – Fecl2 will follow the 18 electron rule because it is a coordination compound.it is similar to the octet rule of a coordination molecule. The electrons that will be needed for the FeCl2 lewis structure will be 8 + (2*8) = 24 because the octet rule required 8 electrons in the valence shell for every atom. We get the available valence electrons are 20 from the previous calculation for FeCl2. Now the required electrons will be (24-20) = 4 electrons and the minimum number of bonds required that all the three atoms should be connected in this molecule is 4/2 = 2 bonds.

Step 3- Now time for deciding on the central atom in the FeCl2 lewis structure. Fe is here central atom as it is electropositive because it is a transition metal, whereas Cl is from the halogen family and it is a more electronegative atom.

Step 4 – Connect two Cl atoms with the central Fe via the minimum number of required single bonds i.e. two. So, Fe makes two single bonds with two Cl atoms from its d orbital electrons in the FeCl2 lewis structure.

Step -5 After the bond formation we have to check the number of lone pairs available over the molecule. So, we check which atoms in the FeCl2 lewis structure contain lone pairs. In the FeCl2 lewis structure, Fe is +2 oxidation state, so it is a d6 system and it has no lone pairs in its d orbital. So, we check the lone pairs over Cl atoms. Cl is group 17th element and from the halogen family. So, after bond formation, it has three pairs of lone pairs. So, the lone pairs are assigned only over the Cl atoms.

All the octet is complete after the bond formation and lone pairs are assigned, so no need to add any kind of multiple bonds in the FeCl2 lewis structure.

2.    FeCl2 hybridization

The bonding method of coordination compound or metallic compound is different. They do not follow the rule of the Valence Bond Theory (VBT). They will follow CFT i.e. Crystal Filed Theory. Hybridization is a corollary of VBT. So, it is difficult to determine the hybridization of FeCl2 lewis structure.

So, we predict the hybridization of FeCl2 lewis structure from its shape. The shape is bent and two surrounding atoms are present and no involvement of lone pairs, so there will be two orbitals are involved in the hybridization and the hybridization will be sp.

In the hybridization, FeCl2 does not involve its d electrons, because they are not it’s outermost orbital and due to the presence of weak field ligand Cl, only the outer orbital will contribute, they are 3s and 4p orbital. So, it is another example of an outer orbital complex like FeCl3.

If we use the typical formula for the calculation of hybridization, H = 0.5(V+M-C+A),

H = ½(2+2+0+0) =2 (sp), Fe has two electrons apart from six electrons in its d orbital and two Cl atoms are present. From VSEPR theory if the number of orbitals mixed in hybridization is 2 then the central atom is sp2 hybridized.

Let us draw and understand the hybridization of the FeCl2 lewis structure.

FeCl2 Hybridization

From the box diagram of Fe(II), we can say that only 4s and 4p orbitals are involved in the bond formation for the FeCl2 lews structure. So, the hybridization is sp. 4s and 4p orbitals are outer orbital for Fe, so it is an outer orbital complex. When it forms tetrahydrates, then four water molecules bind with four unpaired electrons in the d orbital and makes an octahedral complex.

1.    Is FeCl2 ionic or covalent?

The coordination compound is somewhat covalent. But in the FeCl2 lewis structure, Fe and Cl two ions can be separated due to large ionic differences and also show ionic character. In the aqueous solution, it can be ionized easily, and Fe(II) easily polarize chloride anions.  So FeCl2 is ionic besides covalent character.

2.    Is FeCl2 soluble in water?

Any polar molecule will be soluble in a polar solvent (like dissolve like). Water is a polar protic solvent and it can form an H bond also. FeCl2 is a polar molecule because the charge difference between Fe and Cl is so high and due to its bent shape, it makes polar. So, naturally, FeCl2 is soluble in water.

3.      Is FeCl2 aqueous?

After soluble in water any molecule, then that form is called an aqueous form of that particular molecule. As discussed previously that the FeCl2 lewis structure is soluble in water, so after soluble, the whole solution is called an aqueous solution of FeCl2. So FeCl2 can make an aqueous solution easily after being soluble in water.

In the aqueous solution, FeCl2 can easily be ionized to separate the two ionic forms.

FeCl2(aq) = Fe2+ (aq) + 2Cl(aq)

4.    Is FeCl2 a salt?

The reaction between acid and base always gives us salt and water. So, if a molecule is produced after the reaction between an acid and basic molecule then it is called salt. Salt is the combination of counter cation of a basic molecule and counter anion of acidic molecules.

If we reacted ferrous hydroxide with hydrochloric acid we should get FeCl2 as a salt along with water as a side product.

Fe(OH)2 + 2HCl = FeCl2 + 2H2O

So basically, salt is the neutralization part of an acid and base after reaction and salt does not have any acidic as well as basic property in it. So FeCl2 is salt.

5.    Is FeCl2 a strong electrolyte?

A substance that dissolves in water or any other polar solvent to produce ions and a solution that conducts electricity is called electrolytes. In the aqueous solution of FeCl2, we already see that FeCl2 is fully ionized in that solution to form ferrous and chloride ions. Those ions are very good conductors of electricity. So, if we passed the current in the aqueous solution of FeCl2, then it can carry the current in a very good way. So FeCl2 is a strong electrolyte.

Image source Wikimedia

6.    Is FeCl2 a precipitate?

If a compound is insoluble in water then it can be precipitated down the reaction vessel. But FeCl2 is soluble in water so there is no chance for FeCl2 to exist as a precipitate. The precipitate can also form due to the reaction of two compounds and in an aqueous solution, the product will be insoluble in water.

7.    Does FeCl2 react with HCl?

When we reacted Fe with HCl the FeCl2 is formed instead of FeCl3. Because FeCl2 is a thermodynamically more stable product. It is a displacement reaction and metal can easily displace the H2 from HCl, so FeCl2 is formed instead of FeCl3.

Conclusion

FeCl2 is also a coordination compound and it can form tetrahydrates adopting octahedral geometry. Cl is weak filed ligand so the system is sigh spin and Fe is +2 oxidation state. So, the electronic configuration will be d6 high spin. FeCl2 is soluble in water and a strong electrolyte.

Biswarup Chandra Dey

Chemistry is not all about reading line by line and memorize, it is a concept to understand in easy way and here I am share with you the concept about chemistry which I learn because knowledge is worth to share it.

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