HgCl2 Lewis Structure, Characteristics: 23 Quick Facts


HgCl2 is the chemical formula of mercuric chloride. Here, we are discussing about HgCl2 lewis structure, characteristics and quick facts.

Mercuric chloride (HgCl2) is a white solid crystalline powder with no odour. It is a triatomic molecule consists of one mercury atom and two chlorine atoms linearly. HgCl2 is highly toxic in nature. It has some synonyms like sublimate, mercury (ii) chloride, mercury bichloride and Dichloro mercury. The molecular weight of HgCl2 is 271.50.

How to draw HgCl2 lewis structure?

Lewis structure can be drawn with the help of following points listed below:

  1. Firstly note the positions of groups of Hg and Cl atoms in periodic table.
  2. Then count the total valence electrons in available on Hg and Cl atoms.
  3. Most electronegative atom will be the central atom and rather all are bonding to it by forming sigma covalent bond within Hg and two cl atoms.
  4. After forming bonds within Hg and Cl left over valence electrons should get put on the bonding Cl atoms and they are being non – bonding electrons.
  5. Note the number of lone electrons present on HgCl2 lewis structure.
  6. Check whether the Hg and Cl atoms have complete or incomplete octets in Hg Cl2 lewis structure.
  7. Finally, predict the shape and geometry of HgCl2 lewis structure with its hybridization and bond angle.
hgcl2 lewis structure
HgCl2 lewis structure

HgCl2 valence electrons

In HgCl2 lewis structure, there are on Hg atom and two chlorine atoms are present in it structure. Here, the Hg atom belongs to 12th periodic table group and the chlorine atom belongs to 7th periodic table group.

Thus, the Hg atom has two valence electrons in its outer valence shell orbital and the chlorine atoms have seven valence electrons in its outer valence shell orbital. Hence, the overall valence electrons available on HgCl2 lewis structure are:

Valence electrons on mercury (Hg) = 2

Valence electrons on chlorine (Cl) = 7 x 2 (Cl)

Therefore, Valence electrons on HgCl2 lewis structure = 2 + 14 = 16

Hence, total sixteen valence electrons present on HgCl2 lewis structure.

Total electrons pairs on HgCl2 can be calculated by dividing 16 valence electrons by 2.

Thus, HgCl2 total electron pairs = 16 / 2 = 8

So, HgCl2 lewis structure has total eight electrons pairs.

hgcl2 lewis structure
Valence electrons on HgCl2 lewis structure

HgCl2 lewis structure octet rule

HgCl2 lewis structure has total 16 valence electrons present on it. From these 16 valence electrons 4 valence electrons becomes bond pair electron as they are forming two Hg-Cl bonds within one mercury and two chlorine atoms.

Hence, the remaining 12 valence electrons of HgCl2 lewis structure goes on two chlorine atoms and being 12 non – bonding electrons on two chlorine atoms i.e. each chlorine atom has six non – bonding electron. Thus the two chlorine atoms of HgCl2 lewis structure has total eight electrons i.e. two bond pair electrons and six non – bonding electrons.

Therefore, the two chlorine atoms of HgCl2 lewis structure has complete octet. The central mercury (Hg) atom has for electrons i.e. four bond pair electrons. Thus, the mercury atom of HgCl2 lewis structure has incomplete octet. Hence, in HgCl2 lewis structure Hg has incomplete octet and two Cl atoms has complete octet.

Octet rule on HgCl2 lewis structure

HgCl2 lewis structure lone pairs

HgCl2 lewis structure has 16 total valence electrons. From them four electron are bond pair electrons forming two Hg-Cl bonds within central Hg atom and two bonding Cl atoms. The remaining 12 valence electrons are being non – bonding electrons on two Cl atoms of HgCl2 lewis structure.

Here, these 12 non – bonding electrons on two Cl atoms are being six lone electrons pair. Each chlorine atoms contains three lone electron pairs on HgCl2 lewis structure. Therefore, the HgCl2 lewis structure has total six lone pair electrons.

HgCl2 lewis structure formal charge

The stability of any lewis structure depends upon the formal charge present on it. If the formal charge is present on lewis structure, the lewis structure considered to be a stable lewis structure. There is a formula to evaluate the formal charge present on any lewis structure:

Formal charge = (valence electrons – non-bonding electrons – ½ bonding electrons)

The evaluation of formal charge present on HgCl2 lewis structure can be done by evaluating the formal charge present on each Hg and Cl atoms present in HgCl2 lewis structure. Let us calculate the formal charge on HgCl2 lewis structure:

Mercury atom: Mercury atom has valence electrons in HgCl2 = 02

                        Mercury atom has non-bonding electrons in HgCl2 = 00

                           Mercury atom has bonding electrons in HgCl2 = 04 (one bond = 2 electrons)

Mercury atom of HgCl2 lewis structure contains formal charge = (02–00–4/2) = 0

Thus, in HgCl2 lewis structure the mercury atom has zero formal charge.

Chlorine atom: Chlorine atom has Valence electrons in HgCl2 = 07

                         Chlorine atom has Non- bonding electrons in HgCl2 = 06

                            Chlorine atom has Bonding electrons in HgCl2 = 02 (one bond = two electrons)

Chlorine atom of HgCl2 lewis structure has formal charge = (7–6–2/2) = 0

Thus, in HgCl2 lewis structure the chlorine atom has zero formal charge.

Therefore, the Mercury atom and Chlorine atoms in HgCl2 lewis structure has zero formal charge.

HgCl2 lewis structure resonance

In HgCl2 lewis structure all these conditions are not fulfilled. There are only two single sigma covalent bonds are present on HgCl2 lewis structure.

Chlorine atoms have lone electron pairs but sill movement of electrons are not possible to form double or triple bond and also there is no formal charge is available on HgCl2 lewis structure. Hence, the resonance structure of HgCl2 is not possible.

HgCl2 lewis structure shape

The HgCl2 lewis structure is a triatomic molecule, composed of one mercury and two chlorine atoms in which the central mercury atom connected with two chlorine atoms.

Thus, with accord to VSEPR theory, the HgCl2 lewis structure consists of AX2 generic formula in which A is central atom and X is bonding atoms connected to central atom. There is no lone pair electrons present on central Hg atom. Hence, as per the VSEPR theory, the HgCl2 lewis structure has linear molecular shape and linear electron geometry.

HgCl2 lewis structure angle

HgCl2 lewis structure comes under AX2 generic formula of VSEPR theory as the central Hg atom gets linked with two bonding Cl atoms. Thus, HgCl2 lewis structure has linear molecular shape and linear electron geometry.

Also the HgCl2 lewis structure has ‘sp’ hybridization. Hence, the bond angle of HgCl2 is 180 degree. Therefore, the HgCl2 lewis structure has Cl-Hg-Cl bond angle of 180 degree.

Bond angle of HgCl2 lewis structure

HgCl2 hybridization

As the HgCl2 lewis structure composed of three atoms i.e. one Hg and two cl atoms. They all are connected to each other with single covalent bonds and comes under AX2 generic formula of VSEPR theory.

Thus, the HgCl2 lewis structure has linear molecular shape and linear electron geometry. Therefore, according to VSEPR theory the HgCl2 lewis structure has ‘sp’ hybridization.

Why HgCl2 has ‘sp’ hybridization?

HgCl2 molecule consists of three atoms having one mercury atom and two chlorine atoms. The hybridization of any lewis structure can be predicted from its steric number. Here, the HgCl2 lewis structure hybridization can be recognized by the steric number of the central Hg atom.

Steric number is the addition of total bonded atoms joined to the central atom or element and lone electron pairs present on it.

Steric number of HgCl2 = No. of bonding atoms to Hg + lone electron pairs present on Hg atom

Therefore, Hg atom have steric number in HgCl2 lewis structure = 2 + 0 = 2

Hence the HgCl2 lewis structure has 2 steric number and thus the mercury (Hg) atom has ‘sp’ hybridization.

How HgCl2 has ‘sp’ hybridization?

In HgCl2 lewis structure, the Hg atom has electronic configuration at ground state is [Xe], 4f14, 5d10, 6s2. Therefore, the Hg (mercury) atom contains two valence electrons in its outer shell valence orbital. 

Hence, the steric number of Hg atom in HgCl2 lewis structure is 2 + 0 = 2, as there are no lone electron pairs on central Hg atom. Even the HgCl2 molecule has linear molecular shape and electron geometry as per VSEPR theory. Thus, in the HgCl2 lewis structure, the Hg atom is ‘sp’ hybridized due to its geometry of two ‘sp’ hybrid orbitals.

HgCl2 solubility

Mercuric chloride (HgCl2) is soluble in:

  • Water (sparingly soluble)
  • Ether
  • Alkanol (R-OH)
  • Ethyl acetate
  • Acetone
  • Benzene (slightly soluble)
  • Carbon disulphide (CS2) (slightly soluble)
  • Pyridine (slightly soluble)

Why HgCl2 is soluble?

HgCl2 is an binary compound containing one metal atom i.e. Hg atoms and other halogen atom i.e. chlorine atom. Thus, it is considered that all the binary compounds containing halogen atoms and metals (except silver [Ag] metal) atoms are soluble in water and other polar solvents.

Is HgCl2 soluble in water?

Yes, HgCl2 is soluble in water, but it is sparingly soluble in water not completely soluble in water.

Why HgCl2 is soluble in water?

HgCl2 is an binary substance having one metal atom and halogen atom. These kinds of all binary compounds get soluble in water except silver metal. Even if we add the more chlorine to the water then the solubility of HgCl2 compound gets increases.

How HgCl2 is soluble in water?

HgCl2 is sparingly soluble in water, the solubility of HgCl2 increases in water after the addition of more chlorine to the solution and even if it gets heated or warm, the HgCl2 gets completely dissolved. HgCl2 forms a complex compound in water solution after the addition of more chlorine atoms.

HgCl2​ + 2Cl → [HgCl4​]2−

Is HgCl2 polar or nonpolar?

HgCl2 is a non – polar compound. In HgCl2 there are two dipole moments on two chlorine atoms which get cancel out each other, hence HgCl2 is non – polar in nature.

Why HgCl2 is non – polar?

The HgCl2 is a non – polar substance because there is the formation of two dipole moments on two chlorine atoms of HgCl2 molecule. Both the chlorine atoms of HgCl2 pull the electron density towards them away from the centrally placed mercury atom.

Thus, the two dipoles on two chlorine atoms have similar strength and both on opposite direction of central Hg atom. Hence, both the dipole moments get cancel out each other being a HgCl2 is non – polar in nature.

How HgCl2 is non – polar?

The HgCl2 molecule has symmetrical arrangement of in its structure, as it has linear molecular shape and electron geometry. So, the electron cloud generates on two chlorine atoms which stretch this electron cloud in opposite direction of central Hg atom. Hence, HgCl2 is a non – polar molecule.

Is HgCl2 an acid or base?

HgCl2 is behaved as lewis acid, as it is capable of accept electron pairs from other lewis bases or chemical compounds.

Why HgCl2 is a lewis acid?

Lewis acids are the substance which contains empty orbitals and are able to accept electron pairs from other lewis bases. Here, the HgCl2 has the incomplete octet of central Hg atom. Thus it has empty orbitals to accept electrons and hence HgCl2 can behave as lewis acid.

How HgCl2 is a lewis acid?

HgCl2 has pKa value of 3.2 thus it shows more acidity in its character. Also it behaves as a lewis acid when it reacts with a base like ammonia it accepts electron pair from ammonia solution and form Hg-NH2 bond to form HgNH2Cl.

HgCl2(aq) + 2NH3(aq)HgNH2Cl(s) + 2NH4+(aq) +Cl(aq

Is HgCl2 aqueous?

HgCl2 is an white solid crystalline compound and not an aqueous solution. But it can sparingly soluble in water and form aqueous solution. At pH 2 and 4.5 it can form an aqueous solution with HgCl2 when mixed in water. Also its solubility increases by adding chlorine solution to it.

Is HgCl2 ionic?

HgCl2 is not ionic compound rather it is a covalent compound. There are two covalent bonds between Hg and Cl atoms and there is no any positive or negative formal charge is present on HgCl2 molecule. Thus, it is a covalent compound and not ionic.

Is HgCl2 a precipitate?

HgCl2 when reacts with compounds like SnCl2 (stannous chloride) or KI (potassium iodide). When HgCl2 reacts with stannous chloride (SnCl2), the HgCl2 gets reduced as Hg and form Hg2Cl2.

SnCl2 + HgCl2 → Hg2Cl2 + SnCl2

HgCl2 + 2KI → HgI2 + 2KCl (forms orange precipitate of HgI2)

Is HgCl2 a strong electrolyte?

No, HgCl2 is not a strong electrolyte because it is a weak electrolyte as it cannot form more ions when dissolved in water.

Why HgCl2 is weak electrolyte?

Electrolytes are those substance which when get mixed in water can dissociate and form ions to conduct electricity. The HgCl2 is a weak electrolyte, when it mixed in water it can form very less ions as it is sparingly soluble in water. Thus it is not a strong electrolyte but a weak electrolyte.

Conclusion:

Mercuric chloride (HgCl2) has total 16 valence electrons from the 4 are bonding electrons and remaining 12 electrons are non- bonding electrons. Thus it has two Hg-Cl covalent bonds and have total six lone electron pairs. It has zero formal charge. It has linear shape and geometry and sp hybridization and 180 degree bond angle.

Dr. Shruti Ramteke

Hello everyone I am Dr. Shruti M Ramteke, i did my Ph.D in chemistry. I have five years of teaching experience for 11-12 standard, B,Sc and MSc in chemistry subject. I have published total five research articles during Ph.D on my research work and i have fellowship from UGC for my Ph.D. My Masters with specilization Inorganic chemistry and my graduation with chemistry, zoology and environmental science subjects. thank You

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