ZnCl2 Structure & Characteristics (13 Important Facts)


ZnCl2 or zinc Chloride is halogenated salt of Zinc having a molecular weight of 136.286 g/mol. Let us learn about ZnCl2 in detail.

ZnCl2 is a borderline element molecule, it is a d10 system. It is a halogenated salt of the d-block element. The oxidation state of the Zn is +2 and the stable valency of Zn two is maintained here. The molecule has not any crystal field stabilization as the d orbital of Zn is filled with electrons.

ZnCl2 is diamagnetic in nature because the d orbitals filled with 10 electrons and there are no unpaired electrons are present. Now we will discuss hybridization, lewis structure, polarity, and many more of the ZnCl2 with proper explanation in the following section of this article.

1.     How to draw the ZnCl2 structure?

The lewis structure of ZnCl2 can give us a clear idea of the molecular property. Let us discuss how to draw structure of the ZnCl2 in a few steps.

Counting the valence electrons

While drawing the lewis structure of any molecule first of all we should count the total valence electrons of that molecule by counting the valence electrons of the substituent atoms. The total valence electrons for the ZnCl2 are 16 where two are from Zn and 14 are from two Cl sites, so we add them together.

Choosing the central atom

The 2nd  step for lewis structure drawing is selecting the central atom for a molecule among all the substituent atoms. Zn is selected as the central atom here based on the electropositivity and size of the atom. two Cl atoms are present at the terminal atoms in this molecule.

Satisfying the octet

After the bond formation, each atom of a molecule should follow the octet rule by completing its valence orbital with a suitable number of electrons. Zn is a d block element so it needs 10 electrons in the valence orbital and Cl needs 8 electrons to complete the octet. They share electrons while they form a bond.

Satisfying the valency

During the octet formation, each atom should maintain its stable valency based on its oxidation state. Here Zn is +2 oxidation state, so the stable valency for Zn is here 2 and it is maintained because it forms two bonds with two Cl atoms, and each Cl atom is also satisfied by their mono valency.

Assign the lone pairs

The excess nonbonded electrons present in the valence orbital of a particular atom exist as lone pairs. In the ZnCl2 all the valence electrons of the Zn are used in the bond formation so it lacks lone pairs but each Cl has three pairs of lone pairs because only one electron is being used in bond formation.

2.     ZnCl2 structure valence electrons

The valence electrons are counted as those electrons present in the outermost shell of every individual atom. now we count the total valence electrons for the ZnCl2.

The total number of valence electrons for the ZnCl2 molecule is 16. This number is the summation of the valence electrons of the Zn and two Cl atoms. Valence electrons for the molecule are the total number of valence electrons shared by the individual atoms.

  • The valence electrons for the Zn are 2 (as the d orbital is fully completed and two electrons in the 4s orbital)
  • The valence electrons for each Cl atom are 7 (belong to halogen or group 17th element)
  • So, the total number of valence electrons for the ZnCl2 molecule is 2+7+7 = 16

3.     ZnCl2 structure lone pairs

The remaining valence electrons in the outermost orbital are considered lone pairs of the atom. Let us count the lone pairs present over the ZnCl2.

ZnCl2 contains a total number of 12 lone pairs which belong to Cl atoms only not the Zn. Each Cl has six lone pairs of electrons or three pairs because it has seven valence electrons, and after maintaining its mono valency remaining six electrons exist as lone pairs, but Zn has not any.

  • The formula is being used to count the lone pairs = electrons present in the valence shell – electrons involved in the bond formation
  • The lone pairs present over the Zn atom are, 2-2 =0
  • The lone pairs present over each Cl center are, 7-1 = 6
  • So, the total lone pairs over the ZnCl2 molecule are, 6*2 = 12 lone pairs electrons or 6 pairs

4.     ZnCl2 structure shape

The molecular shape is a particular shape adopted by the molecule after the bond formation among constituent atoms. Let us predict the shape of the ZnCl2.

ZnCl2 adopts the linear geometry around the central Zn atom and both Cl atoms are present in the same plane of the molecule, which can be considered in the following table.

Molecular
Formula
No. of
bond pairs
No. of
lone pairs
Shape  Geometry    
AX10Linear  Linear
AX2        20Linear  Linear  
AXE       11Linear  Linear  
AX330Trigonal
planar
Trigonal
Planar
AX2E     21BentTrigonal
Planar
AXE2     12Linear  Trigonal
Planar
AX440TetrahedralTetrahedral
AX3E     31Trigonal
pyramidal        
Tetrahedral
AX2E2                2BentTetrahedral
AXE3                     13Linear  Tetrahedral
AX550trigonal
bipyramidal
trigonal
bipyramidal
AX4E     41seesawtrigonal
bipyramidal
AX3E2    32t-shaped         trigonal
bipyramidal
AX2E3    23linear   trigonal
bipyramidal
AX660octahedraloctahedral
AX5E     51             square
pyramidal   
octahedral
AX4E2                    42square
pyramidal 
octahedral
VSEPR Table
ZnCl2 Molecular Shape

Transition metal element having filled d orbital or d10 atom always form linear molecule because it has not any crystal field stabilization, so due to avoiding the steric crowding, it forms linear geometry. For the linear geometry, its hybridization should be sp for the central atom.

5.     ZnCl2 structure angle

The bond angle is the angle made by the constituent atom with the central atom for proper orientation. Let us calculate the bond angle for the ZnCl2 molecule.

The bond angle for the linear molecule is 1800, being a linear molecule the bond angle for the ZnCl2 is the same. This value of angle can be predicted by the VSEPR (Valence Shell Electrons Pair repulsion) theory, even from the hybridization value bond angle will be calculated.

ZnCl2 Bond Angle
  • The bond angle formula according to Bent’s rule is COSθ = s/(s-1).
  • The central atom Zn is sp hybridized, so the s character here is 1/2th
  • So, the bond angle is, COSθ = {(1/2)} / {(1/2)-1} =-(1)
  • Θ = COS-1(-1) = 1800
  • So, the bond angle for the ZnCl2 is 1800 is being calculated.

6.     ZnCl2 structure hybridization

Atomic orbitals of different energy undergo hybridization to form equivalent energy-containing hybrid orbitals. Now we explore the hybridization of the ZnCl2.

The central Zn is sp hybridized in the ZnCl2 molecule as its d orbitals are filled, which can be confirmed by the following table.

Structure   Hybridization
value  
State of
hybridization
of central atom
Bond angle
1.Linear         2         sp /sd / pd1800
2.Planner
trigonal      
3sp2                   1200
3.Tetrahedral 4sd3/ sp3109.50
4.Trigonal
bipyramidal
5sp3d/dsp3900 (axial),
1200(equatorial)
5.Octahedral   6        sp3d2/ d2sp3900
6.Pentagonal
bipyramidal
7sp3d3/d3sp3900,720
Hybridization Table
  • We can calculate the hybridization by using the formula, H = 0.5(V+M-C+A),
  • So, the hybridization of central Zn is, ½(2+2+0+0) = 2 (sp)
  • One s orbital and one p orbital of Zn is involved in the hybridization.
  • The lone pairs of Cl are not involved in the hybridization.

7.          Properties of ZnCl2

The physical properties are those which cannot be changed during the chemical reaction of the molecule. Let us know the physical properties of ZnCl2.

Physical Properties Magnitude
Molecular weight          136.29 g/mol
Melting point    2900 C
Boiling point7320 C
Density      2.97 g/cm3
Solubility in water   432 g / 100 g water
Odor      odorless
Color white
Physical Properties of ZnCl2

Those are the basic physical characteristics of ZnCl2, apart from these, it has many chemical properties when it reacts with proper reagents.

8.     ZnCl2 solubility

The solubility of ZnCl2 is various solvents observed but in water, it has greater solubility than other solvents. Let us discuss the solubility of ZnCl2.

ZnCl2 has a greater solubility in water because it has a partial ionic character and due to the size mismatching Zn and Cl bonds easily break in water solution and gets dissolved in it. The Chloride ions also form H-bonding with water to increase its solubility to another aprotic solvent.

Apart from water, ZnCl2 can be soluble in the following solvents

  • Ethanol
  • Acetone
  • Glycerol

9.     Is ZnCl2 solid or liquid?

The physical state or nature of a molecule depends on the constituents present in to it and also temperature. Let us see whether ZnCl2 is solid or liquid.

ZnCl2 is solid in nature because it is made by strong ionic force in between the atoms. The van der Waal’s force of attraction is very high for this molecule, it exists as a solid white powder. The lattice structure of the crystal is a zinc blend, so it has a strong internal force and exists as a solid at room temperature.

It is a crystalline solid molecule and the hydrated part of the molecule exists in the lattice structure.

10. Is ZnCl2 polar or nonpolar?

If there is a resultant dipole moment is present then the molecule is said to be polar otherwise not. Let us check whether ZnCl2 is polar or nonpolar.

ZnCl2 is a non-polar molecule and the main reason behind its non-polarity is the shape of the molecule. Due to its linear shape, the dipole-moment from Zn to both Cl are the same in magnitude but opposite in direction, so they cancel out each other, and there is zero resultant dipole-moment for the molecule.

ZnCl2 Dipole-Moment Direction

11. Is ZnCl2 acid or base or salt?

A molecule is an acid or base depending on the value of pH, again it is formed by the reaction of acid and base then it will be salt. Let us see the nature of ZnCl2.

ZnCl2 is a salt because it formed by the cation and anion other than H+ and OH and also there is ionic interaction is present in the molecule. Also, it is prepared by the reaction of zinc hydroxide and hydrochloric acid, so it is made by the reaction of acid and base, so it is a salt.

It is a good lewis acid because it can accept electrons in its vacant orbital from electron rich centre.

12. Is ZnCl2 electrolyte?

If a substance carries electricity through an aqueous solution by dissolving in it, is called an electrolyte. Let us see whether ZnCl2 is an electrolyte or not.

ZnCl2 is an electrolyte because it gets dissociated with ions in the aqueous solution by full hydrolysis. After ionization it formed Zn2+ and 2Cl ions, those ions are highly charged particles, cation contains +2 charge, and chloride ions are highly electronegative, so they can carry electricity through the solution very quickly.

On the other hand, we can say that as ZnCl2 is salt so it can carry electricity and behaves as an electrolyte.

13. Is ZnCl2 ionic or covalent?

Ionic or covalent nature is depending on the theory of polarizability of Fajan’s rule, each molecule has both characteristics. Let us see whether ZnCl2 is ionic or covalent.

ZnCl2 is an ionic molecule because there is strong ionic interaction occurring between highly electropositive Zn2+ and highly electronegative Cl atoms. The size of Zn2+ is very small s it contains 10 d electrons, so it has a higher ionic potential and it can easily polarize the Cl ions having polarizability.

But it has some covalent character because it is formed via hybridization also.

14. Is ZnCl2 an inorganic compound?

Apart from all the hydrocarbons, all the molecules consisting of different atoms are known as inorganic compounds. Let us check if ZnCl2 is an inorganic compound or not.

ZnCl2 is an inorganic compound because it is made by the Zn and Cl which are different from hydrocarbon. C and H-containing molecule is referred to as hydrocarbon but here the molecule is the absence of those atoms, so it is a pure inorganic compound and it has various inorganic characteristics.

Conclusion

ZnCl2 is an inorganic neutral salt. It is a compound of d block element and has a filled d orbital by electrons, so there is no charge transfer occurring due to d-d- transition. That’s why it exists white in color. It is also a good lewis acid because it can accept electrons in the vacant orbital of Zn and is used in many organic reactions.

                                                                                             

                                                                             

                                                                                                                 

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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