FeCl3 Lewis Structure, Characteristics:13 Facts You Should Know


Let us talk about FeCl3 lewis structure and 13 important characteristic features of FeCl3 in this article.

FeCl3 is the chemical formula of ferric chloride. The Central Fe is in a +3 oxidation state here. So, the Fe is named ferric. Cl is not here present as a counter ion also it acts as a ligand here, cause FeCl3 is a coordination compound rather than a covalent molecule. So, it has different coordination properties along with covalent properties. The molecular shape is trigonal planar but in coordination chemistry, it adopts octahedral geometry, the vacant site is filled with a water molecule causing ferric chloride to exist as a crystal form.

Cl here acts as a weak filed ligand, so no electrons in d orbital exist as paired form. It is a high spin complex. Fe(III) is a d5 system and all the electrons exist single spin only with no paired form. FeCl3 molecule can be fully ionized by charge separation of ferric and chloride.

1.    How to draw FeCl3 lewis structure?

Drawing of lewis structure of coordination compound is very difficult because it does not follow the general rule of the covalent molecule. Because this is a coordination molecule and it has some coordination property in it. Lewis dot structure can give us a proper picture of the molecular shape, valence electrons, etc. A few steps are there in the drawing of the lewis dot structure.

Step 1– At first, we count the valence d electrons for Fe and p electrons for Cl atoms and added together. In the FeCl3 lewis structure, the valence electrons for Fe are 5 as it is in a +3 oxidation state, and all the electrons from its d orbital only, for three Cl atoms is 7*3 = 21. So, the total valence electrons are 5+21 = 26.

Step 2 – Being a coordination compound FeCl3 will follow the 18 electron rule it is like the octet rule of a coordination molecule. The electrons that will be needed for the FeCl3 lewis dot structure will be 8 + (3*8) = 32 because the octet rule required 8 electrons in the valence shell for every atom. The available valence electrons are 26 from the previous calculation we get. Now the required electrons will be (32-26) = 6 electrons and the minimum number of bonds required that all the four atoms can be connected in this molecule is 6/2 = 3 bonds.

Step 3– Now time for choosing the central atom. Fe is here central atom as it is electropositive metal and its size is comparatively large. Because Fe is a transition metal and metal shows electro positivity where Cl is from the halogen group and it has more electronegativity.

Step 4 – Connect all the atoms with the central atom Fe via the minimum number of required single bonds i.e. three. So, Fe makes three single bonds with three Cl atoms from its d orbital electrons.

Step 5– Now calculate the number of lone pairs and their position of them. Fe is a group d element and it is +3 oxidation state in FeCl3 so it is a d5 system, and all the five electrons are present at the five subsets of the d orbital so it has no lone pairs. Cl belongs to the halogen family also it is group 17th element and it has seven electrons in its valence shell and only one electron is involved in the bond formation so, the rest six electrons are assigned as three pairs of lone pairs. Three Cl atoms contain three pairs of lone pairs.

2.    FeCl3 lewis structure shape

The shape of any coordination molecule depends on the coordination number of the central metal atom. The structure may be varying cause some metal center can expand their coordination number. But in the covalent molecule, it depends on the VSEPR theory.

FeCl3 Shape

In FeCl3 lewis structure, Fe is +3 oxidation state, so it has 5 d electrons and this is the valence electrons for Fe(III). Now three Cl atoms, each contribute one electron, and all three contribute three electrons. Now total electrons count for the FeCl3 lewis structure will be 5+3 =8 electrons. According to the VSEPR (Valence Shell Electrons Pair Theory), the molecule AX3 adopts tetrahedral geometry having lone pair over the central atom if the electrons count will be 8. Again, from coordination chemistry, the molecule will be tetrahedral if the coordination number will be 4.

But here the scenario is different. Neither the coordination number of Fe(III) is 4 nor does it contain any lone pairs. So, the shape is decided by the surrounding atoms and there are three surrounding atoms present and the best acceptable shape will be trigonal planar.

3.    FeCl3 valence electrons

Although FeCl3 is a coordination compound it has also valence electrons. Fe and Cl separately have a certain number of valence electrons. There will be some electrons present in the outermost orbital or valence orbital of Fe and Cl atoms.

FeCl3 Valence Electrons

Iron is a 4th-period element. It is also a d block element which means the outermost orbital of Fe is the d orbital. In the FeCl3 lewis structure, Fe is +3 oxidation state, so its electronic configuration becomes 3d5. So, it has five electrons in its d orbital. D has five subsets and Cl is a weak field ligand. So, every subset contains one unpaired electron. So, iron has five valence electrons.

Now for Cl, it belongs to the halogen family that is group 17th element. So, naturally, it has seven electrons in the valence shell. Three Cl atoms have 3*7 =21 valence electrons.

So, the total number of valence electrons in the FeCl3 lewis structure is 5+21=26 electrons.

4.    FeCl3 lewis structure formal charge

Each molecule has a formal charge may be the value will be zero for a neutral covalent molecule but there is some value over a particular ion if that ion possesses ionic character. Even in coordination molecule also shows the formal charge.

The formula we can use to calculate the formal charge of any covalent or coordination molecule is,

F.C. = Nv – Nl.p. -1/2 Nb.p.

Where Nv is the number of electrons in the valence shell or outermost orbital, Nl.p is the number of electrons in the lone pair, and Nb.p  is the total number of electrons that are involved in the bond formation only.

Remind that we always consider the same electronegativity for atoms to calculate the formal charge of a molecule.

In the FeCl3 lewis structure, we have to calculate the formal charge separately for Fe and Cl.

The formal charge over Fe is, 6-0-(6/2) =+3

Iron has a 3d6 system in transition metal cause 4s electrons we cannot consider due to strong ionization energy.

The formal charge over Cl is, 7-6-(2/2) = 0

This result implies that Fe is in a +3 oxidation state which means it has a +3 charge over it and the formal charge also Fe is +3 here.

So, we can conclude that formal charge also predicts the ionic nature or amount of charge of every single atom in a particular molecule.

5.    FeCl3 lewis structure angle

In a covalent molecule bond angle depends on the VSEPR theory or hybridization value but in coordination com pound bond angle depends on the coordination number of a central metal atom or several ligands present in it.

FeCl3 Bond Angle

In the FeCl3 lewis structure, there are three ligands present surrounding the Fe center. So, the geometry according to one metal center and three surrounding ligands will be trigonal planar is perfect. All the ligands have the same and equivalent so no need to adjust their position by changing the bond angle. We know that the bond angle of a trigonal planar geometry shape is 1200.

So here the Cl-Fe-Cl bond angle is expected to be 1200. The lone pairs over Cl are not a problematic situation here so no need for the deviation of bond angle. Again, Cl is weak filed ligand, so Fe is high spin here and the geometry and bond angle are solely decided from the ligand site only and the bond angle is 1200.

6.    FeCl3 lewis structure octet rule

Every atom will follow the octet rule and try to complete its valence shell after the bond formation in a covalent molecule. But in coordination compound will follow the 18 electrons rule. It is like the octet rule of the organometallic complex.

FeCl3 Octet

In the FeCl3 lewis structure, Cl is halogen so it has completed its octet by accepting one electron in its valence shell as it has already seven electrons in it. During the bond formation with Fe, one electron from Cl and one d electron from Fe site share to form a covalent or coordination bond. Thus, the Cl atom completes its octet.

But in the case of Fe, it is a d block transition element, so it should follow the 18 electron rule rather than an octet. In FeCl3 lewis structure, Fe is in a +3 oxidation state so it has 5 d electrons in its valence shell and accepts 3 more electrons from three Cl atoms via sharing to complete its octet. Fe has 26 electrons and deducted from 18 electrons rule it ahs 8 electrons and this is how it can complete its octet.

7.    FeCl3 lewis structure lone pairs

In the FeCl3 lewis structure, there are only present lone pairs over 3 Cl atoms only. Fe does not contain any lone pair. The valence electrons of Fe are 4s orbital and after bond formation, the electrons of d orbital did not participate in the valence shell.

FeCl3 Lone Pairs

Being halogen Cl belongs to group 17th. So, it has seven electrons in the outermost 3s and 3p orbitals. But after the bond formation, there are six electrons present and they exist as three pairs of lone pairs (one in 3s orbital and the other two in 3p orbital).

But in the case of Fe, the outermost orbital is 4s, but in Fe(III) the valence shell is 3d, where five electrons are present in five different subsets. After the bond formation with three Cl atoms rests two electrons do not pair up because of the higher exchange energy of the 3d orbital, so Fe does not contain lone pairs.

8.      FeCl3 lewis structure resonance

For resonance, we need the electron-rich center or any atom which contains more electrons clouds that can be delocalized in different skeletons of that particular molecule. Both are absent in the case of FeCl3 lewis structure.

In the FeCl3 lewis structure, Fe is d block metal so it possesses a positive charge, so it is lack electron density. Again, Cl is more electronegative so it cannot release the electron density from it. So there is no resonance occurs in the FeCl3 lewis structure.

9.    FeCl3 hybridization

For any coordination molecule, it is very difficult to find out its state of hybridization. Because they are violated valence bond theory. So, we cannot find out the hybridization of such a compound.

But if we consider its shape so it can say that as it adopts trigonal planar structure then it should be sp2 hybridized. But Fe is a 3d element so it does not has 3s orbital form bond formation. So, we consider the 4s and 4p orbital here.

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

H = ½(3+3+0+0) =3 (sp2), Fe has three electrons apart from five electrons from the d orbital and three Cl atoms are present. From VSEPR theory if the number of orbitals mixed in hybridization is 3 then it is sp2 hybridized.

As 4s and 4p orbitals are involved here so it is called the outer orbital complex.

Lets us draw and understand the hybridization of the FeCl3 lewis structure.

FeCl3 Hybridization

So, from the box diagram, we can say that the s and p orbitals which are involved in the hybridization are 4s and 4p, and outer electrons only contribute so the complex is the outer orbital complex.

10.    FeCl3 solubility

Fecle3 is soluble in the following solution,

  • Water
  • Ethanol
  • Methanol
  • Acetone
  • diethyl ether

11.    Is FeCl3 ionic?

Yes, FeCl3 is an ionic molecule, as it is a coordination compound but it can be ionized as Fe3+ and Cl. So FeCl3 lewis structure is an ionic molecule.

12.    Is FeCl3 acidic or basic?

FeCl3 is a good Lewis acid. In the FeCl3 lewis structure, we can see that Fe is +3 oxidation state and it has five electrons in the d orbital and the highest number of electrons accumulated by the d orbital is 10. So, it can accept electrons in its d orbital so it acts as lewis acid.

13.    Is Fecl3 polar or nonpolar?

FeCl3 is a polar molecule. Most of the ionic molecules will be polar and FeCl3 is ionic so it has polarity. The electronegativity difference between Fe and Cl is very high so there is a dipole moment generated and it makes polar.

14.    Is FeCl3 tetrahedral?

No, FeCl3 is not tetrahedral, because there are no lone pairs on the  Fe center. It is a trigonal plannar shape.

15.      Is FeCl3 linear?

No, FeCl3 is not linear it is a trigonal planar shape. In the lattice crystal, it is octahedral.

Conclusion

FeCl3 is a coordination compound rather than a covalent molecule. It has coordination property and Cl is not a counter ion here it is a weak filed ligand thus it makes the bond with a higher oxidation state of Fe like Fe(III).

Biswarup Chandra Dey

Hi......I am Biswarup Chandra Dey, I have completed my Master's in Chemistry. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.

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