Arsenic pentachloride (AsCl5) features a central arsenic (As) atom with 5 valence electrons, each forming a single bond with five chlorine (Cl) atoms, contributing 7 valence electrons each. The Lewis structure shows five single As-Cl bonds, using 40 valence electrons, with no lone pairs on arsenic. AsCl5 adopts a trigonal bipyramidal geometry, with three Cl atoms in equatorial positions and two in axial positions, resulting in 90° and 120° bond angles. The molecule’s symmetry makes it nonpolar, despite the polar As-Cl bonds due to the electronegativity difference (As: 2.18, Cl: 3.16). This structure influences its reactivity and use in research, though it’s less stable and common than AsCl3.
Arsenic pentachloride,AsCl5 is a chemical compound formed by arsenic and chlorine. Arsenic chloride has similiar structure like phosphurus pentachloride but has no stable existence.
How to draw AsCl5 Lewis structure ?
The Lewis dot structures are drawn to get facts related with the bonding in molecules and ions. This mainly deals with the shared pairs of electrons between the atom and the octet rule. While drawing lewis structure only the valence electrons are considered. The valence electrons are denoted as dots in lewis structures. So the structures drawn with the help of this concept is called lewis dot structures.
The lewis structure of Arsenic pentachloride or AsCl5 can be drawn easily. Before that it is important to understand how the compound is formed. The atomic number of arsenic is 33 and chlorine is 17. The valence electrons present in the outer shell of arsenic is 5.
The electrons present in the valence shell of chlorine is 7. Here there are 5 chlorine atoms so the total number of valence electrons of five chlorine atoms is 35. Arsenic pentachloride is a covalent compound formed by the mutual sharing of atoms between one arsenic and five chlorine atoms. So the lewis structure of Arsenic pentachloride can be drawn like this
AsCl5 Resonance structure
Resonance is the movement of electrons delocalised in an atom of a molecule. This is mainly depicted through some contributing structures. Such structures or figures are called as its resonance structures. The resonance structure of arsenic pentachloride is same as its shape. There is no delocalistion of electrons takes place here in this case.
AsCl5 Shape
Arsenic pentachloride is formed by the sharing of five valence electrons of arsenic with five chlorine atoms. The shape of the compound is found to be triagonal bipyramidal structure. There are five bonds between arsenic and chlorine.
The two bonds are axial bonds and the remaining three is equatorial bonds. The bond length of axial bonds are greater than the equatorial bonds. The bond length of axial and equatorial bonds are 220.7 pm and 210.6 pm respectively.
AsCl5 Formal charge
Formal charge is a charge assigned to an atom when all of its valence electrons are perfectly shared with other atoms to form a chemical bond.
Formal charge of a molecule can be given as,
Formal charge of an atom = [No. of valence electrons –( No. of electrons + No.of bonds formed)].
The total number of valence electrons present in Arsenic is 5, the lone pair of electron in As is 0, the number of bonds formed by arsenic with five chlorine atoms is 5. So the formal charge of As can be
Formal charge of Arsenic = 5-0-5
= 0
The number of valence electrons present in Chlorine is 7, the electrons available as lone pairs in Cl is 6, the number of bonds formed with one arsenic is 1. So the formal charge of Cl will be
Formal charge of Chlorine = 7-6-1
= 0
The formal charge present in Arsenic and chlorine in AsCl5 is 0.
AsCl5 Bond Angle
The Bond angle in a molecule is the angle between the bonds of atoms when different or same atoms combine together to form a compound. AsCl5 is a compound with five bonds between arsenic and five chlorine atoms with triagonal bipyramidal structure. The bond angle of equitorial bonds in AsCl5 is 1200 and axial bond is 900 respectively.
AsCl5 Octet rule
The octet rule explains that the atoms are found to be very stable when their valence shell or outermost shell are filled with eight electrons. In the case of arsenic penta chloride there is one arsenic atom and five chlorine atoms are present.
The valence shells of each chlorine atom has 7 electrons when it forms five bond with arsenic then the valence shell of each of chlorine atom has eight electrons. So the octet of chlorine atoms in AsCl5 is completely satisfied hence it obeys octet rule. While in arsenic its valence shell contains five electrons and need three more to satisfy the octet rule.
But when it forms five bonds with chlorine atoms its valence shell is now filled with ten that is more than eight electrons. So arsenic shows deviation from octet rule. Hence arsenic is considered as a hypervalent molecule.
A hypervalent molecule is a molecule with one or more elements which has more than eight electrons in its valence shell due to bond formation with other atoms.
AsCl5 Lone pair of electrons
Lone pair of electrons are the electron pair present in the outermost shell of an atom that is not shared or get bonded to another atom. It can be also called as non bonding electron since it doesn’t took part in a bond formation.
The lone pair of electron in a molecule can be found out through the following equation.
Lone pair of electron in an atom = ( No. of valence electrons – No. of electrons shared by the atom) /2
Lone pair of electron in As = (5 – 5)/2
= 0
There is no lone pair in Arsenic atom in Arsenic pentachloride
Lone pair of electron in Cl = (7-1)/2
= 3
The lone pair of electrons in Chlorine is 3. Here there are five chlorine atoms each with three lone pair of electrons.
AsCl5 Valence electrons
Valence electrons are the electrons present in the outermost shell of an atom. Valence electrons participate in a chemical reaction by sharing the electrons to form stable compounds. Before bond formation arsenic has five and chlorine has seven valence electrons in the outermost shell.
After the bond formation arsenic has ten electrons in its valance shell and each chlorine atoms has eight valence electrons in its outermost shell. So the total number of valence electrons present in arsenic chloride is 40.
AsCl5 Hybridisation
The intermixing of atomic orbital with slightly different energy to form a set of new orbitals with same energy and shape is called Hybridisation. This concept gives a good picture about the bond formation in covalent compounds. The number of hybrid orbitals formed will be equal to the number of atomic orbitals got hybridised.
The freshly formed those orbitals are called as hybrid orbitals.
The ground state electronic configuration of Arsenic is 3d10 4s2 4p3. In its excited state electronic configuration is 4s1 4p3 4d1. One of electron in the 4s is excited to 4d level.
One 4s, three 4p and one 4d orbitals hybridise together to form five sp3d hybrid orbitals with same energy. The five chlorine atoms shares one electron present in its 3p orbital to form five covalent bonds. So the hybridisation in AsCl5 is sp3d hybridisation.
AsCl5 Solubility
Since AsCl5 is unstable compound its solubility is not found out.
Is AsCl5 is Acidic or Basic ?
The acidic or basic character of arsenic pentachloride is doesn’t determined due to its unstable nature.
Is AsCl5 Ionic or Covalent ?
A covalent bond is formed by the mutual sharing of electrons between the bonded atoms. Arsenic pentachloride is formed by through sharing of electrons between arsenic and five chlorine atoms. Therefore Arsenic pentachloride AsCl5 is a covalent compound.
Is AsCl5 Polar or Non polar ?
Arsenic pentachloride is a covalent compound with non – polar nature.
Is AsCl5 triagonal bipyramidal ?
Arsenic pentachloride is a compound with triagonal bipyramidal geometry with two axial and three equatorial bonds.
Why is AsCl5 Unstable ?
Arsenic pentachloride is unstable. It due to the incomplete shielding of the 4p orbitals seen in between the nucleus and 4s orbital. Because of this reason electrons of 4s orbital are less available for bonding. Therefore it is unstable in its nature.
Conclusion
This article explains about full details regarding Arsenic pentachloride, a chemical compound. Its lewis structure, valence electrons, lone pairs, octet rule were discussed here. Inaddition to this its shape,solubility and polar nature are explained. Arsenic pentachloride is a compound with sp3d hybridisation with least stability.
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Hi… I am Aparna Dev, a chemistry Postgraduate with a good understanding of chemistry concepts. I am working in Kerala Minerals and Metals Limited Kollam with experience in the development of electrocatalysts as a part of post graduate thesis.
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