Aluminum sulfide (Al2S3) consists of two aluminum (Al) atoms, each with 3 valence electrons, and three sulfur (S) atoms, each with 6 valence electrons. The Lewis structure shows ionic bonds, with Al atoms losing electrons to form Al³⁺ ions and S atoms gaining two electrons each to form S²⁻ ions. In Al2S3, each Al³⁺ ion is surrounded by six S²⁻ ions in an octahedral coordination, and each S²⁻ ion is surrounded by four Al³⁺ ions in a tetrahedral coordination, resulting in a crystalline structure. This ionic arrangement is key to understanding Al2S3’s high melting point and electrical insulating properties.
How to draw the Al2S3 Lewis structure?
Lewis structure is the structural representation. Where the dot represents the no of electrons and dot pair, and line represents a covalent bond. Let us draw Lewis structure.
Bonding and valence electrons of Al2S3
Find out the total number of valence electrons by adding all the outermost electrons of all the aluminium and Sulphur atoms. Al2S3 has strong ionic bonding due to donating and accepting electrons between (Al) metal and (S) non-metal atoms.
Lone pairs and octet rule of Al2S3
After bond formation count the remaining electrons which are not participate in bond formation are denoted as lone pairs of Al2S3 molecule. Also, by applying the octet rule find out whether Al and S atoms complete their octet or not.
Determine the formal charge
The formal charge for aluminium and sulphur atoms can be calculated by applying the given formula for the formal charge. Also shape of the molecule can be determined from the Lewis structure of the Al2S3 molecule.
Al2S3 Lewis structure shape
Lewis structure shape determines the special or definite arrangement of atoms present in the molecule. Let us describe the shape of the Al2S3 molecule.
Lewis structure shape of Al2S3 is trigonal planer because it has 3 valence shell electron pairs. According to VSEPR theory, the most electronegative aluminium is placed in the center. While 3 valence electrons form an ionic bond with the sulphur atom.
Al2S3 Lewis structure formal charge
Lewis structure formal charge is calculated using the formula which includes no. of valence electrons, bonding electrons & nonbonding electrons. Let us calculate the formal charge.
The formal charge of the aluminium atom and sulphur is +3 and -2 respectively. Which can be calculated as, formal charges of lewis structure = (valence electrons – nonbonding electrons -1/2 bonding electrons).
The formal charge of the Al atom in Al2S3 = 3-0-0/2 = +3
The formal charge of the S atom in Al2S3 = 6 – 8 – 0/2 = -2
Al2S3 Lewis structure angle
Lewis structure bond angle is the angle formed by the covalent bond form in between the atom. Let us see the bond angle form in the Al2S3 molecule.
Lewis structure bond angle of Al2S3 is found to be 120o. The ionic bond is formed by a central aluminium atom with two sulphur atoms due to the loss of 3 electrons. Thus S-Al-S has a 1200 bond angle.
Al2S3 Lewis structure octet rule
Octet rule states that the atoms in the Al2S3 must contain 8 electrons in its valence shell so that it should be electronically stable. Let us discuss the octet rule in Al2S3.
In the Al2S3 Lewis structure, all three sulphur atoms complete their octet by accepting 3 electrons from the aluminium atom. And aluminium atom has vacant orbital they donate all electrons to 3 sulphur atom & acquired +3 charge.
Three sulphur atoms gain 2 electrons each from aluminium atom & have -2 charge on sulphur. Thus, each sulphur atom is surrounded by 8 electrons and completes its octet.
Al2S3 Lewis structure lone pairs
Lone pairs of electrons are the unshared electron pairs which are not participating in bond formation. Let us find out the lone pairs on Al2S3.
Al2S3 Lewis structure has 6 lone pairs. It has a total of 24 valence electrons in Al2S3. 12 electrons are being bond pairs which form two single bonds and double bonds between Al and S. Remaining 12 electrons are placed on 3 Al atoms.
Al2S3 valence electrons
The number of outermost electrons present on the atom which are participating in bond formation is valence electrons. let us determine valence electrons in Al2S3.
Al2S3 has a total of 24 valence electrons. The aluminium metal was placed in the 13th group of the periodic table while sulphur non-metal belongs to the 16th group of the periodic table. Hence aluminium has 3 and S has 6 valence electrons in their last orbital.
- Valence electrons of Al atom = 3 X 2 (Al) = 6
- Valence electrons of S atom = 6 x 3(S) = 18
- Total number of valence electrons = 18+6 = 24
- Hence total of 24 valence electrons are present in the Al2S3 molecule.
Al2S3 hybridization
Hybridization is the process in which the mixing of atomic orbital forms a new hybrid orbital. Let us find out the hybridization in the Al2S3 molecule.
Hybridization of aluminium sulphide (Al2S3) is sp2. Which can be determined by the following formula.
Hybridization = no. of σ bond on central atom + lone pair on the central atom.
- No. of σ bond on Al atom = 3
- No. of lone pair on Al = 0
- Therefore, Hybridization of Al2S3 = 3+0 = 3 i.e., sp2 hybridization.
Is Al2S3 solid?
Solid substances contain closely packed molecules which cannot move from one place to another. Let us see whether Al2S3 is solid or not.
Al2S3 is a Gray solid compound. All the molecules of aluminium and sulphur are arranged closely. which has closely packed molecules. It has a rotten egg-like sulphur atom smell. It shows a repeating hexagonal pattern of Al3+ and S2- ions hence Al2S3 has a closely packed hexagonal crystal structure.
Is Al2S3 soluble in water?
The solubility of any compound depends upon the ability of that solute to dissolve in the solvents like water or any other. Let us see the solubility of Al2S3.
Al2S3 is not soluble in water. When dissolved in water decomposes and forms hydrogen sulphide (H2S). It does not contain hydrogen bonds between the atoms present in the molecule.
Is Al2S3 polar or nonpolar?
The polar nature of any compound depends upon the electronegativity difference between the atoms present in the molecule. Let us look at whether Al2S3 is polar or nonpolar.
Al2S3 is ionic polar in nature. As the electronegativity of S is more than Al hence it attracts electron pairs involved in a bond towards itself and develops a negative charge. While aluminium is electropositive donates electrons to Al and acquires a positive charge.
How and Why Al2S3 is polar?
Al2S3 is polar because its atom creates a dipole moment in the molecule. As aluminium is less electronegative than sulphur atoms thus electron clouds are attracted toward more electronegative sulphur atoms. Partial +ve charge on Al and partial – ve charge on S shows that it is polar in nature.
Is Al2S3 molecular compound?
A molecular compound contains a strong covalent bond between the atoms in the molecule. Let us see whether Al2S3 is molecular or not.
Al2S3 is not a molecular compound. it is an ionic compound with Al3+ and S2- ions. It has a strong ionic bond in the Al2S3 molecule.
Is Al2S3 acid or base?
The substances which can donate proton is acids while the substance which accepts proton is base. Let us find out whether Al2S3 is acid or base.
Al2S3 is acid as well as base means amphoteric in nature. It is an amphoteric sulphide which contains sulphide ions. It is formed by metal and nonmetal hence when Al2S3 reacts with a base it forms acid and when reacts with acid forms a base.
Is Al2S3 electrolyte?
Electrolytes are substances which dissociate into ions these ion conducts electricity. Let us discuss whether Al2S3 is an electrolyte or not.
Al2S3 act as an electrolyte. It is made up of Al metal and S non-metal which is ionic in nature. It can itself get dissociated into Al3+ & S2– ions which carry electricity. Al3+ ions go towards the cathode due to the reduction reaction. And S2- ions go towards the anode due to oxidation reaction.
Is Al2S3 salt?
Salts are compounds which are formed by the reactions between acid and base. Let us find out whether Al2S3 is salt or not.
Al2S3 does not act as salt. Because it cannot form the acid-base reaction. It is formed by the reaction between Al metal and S non-metal.
Is Al2S3 ionic or covalent?
Ionic bond form by the weak electrostatic force of attraction while covalent compound form by the strong covalent bonds. Let us see if Al2S3 is ionic or covalent.
Al2S3 is ionic in nature. When aluminium which is a metal and sulphur which is a non-metal combine to form an Al2S3 molecule. Upon dissociation, Al2S3 ionizes intoAl3+ and S2- ions and shows an ionic nature.
Conclusion
Al2S3 Lewis structure has 24 valence electrons and 6 lone pair of electrons. It shows trigonal planer geometry with sp2 hybridization and 120o bond angle. It has a +3 formal charge on aluminium and -2 formal charge on sulphur.
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Hi….I am Darshana Fendarkar, I have completed my Ph.D. from the University of Nagpur. My area of specialization is Inorganic Chemistry.
I have an experience as a Chemist at Earthcare Pvt. Ltd. Also I have 2 years of experience in teaching. Currently, I am working with Lambdageek as a Subject Matter Expert.
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