Aluminium chloride (AlCl3) Lewis structure
Aluminium chloride (AlCl3) lewis structure contains one Aluminium atom and three chlorine atoms. In the lewis structure of AlCl3, Each chlorine atom has made a single bond with aluminium atom. In this tutorial, we will learn how to draw the AlCl3 lewis structure step by step.
AlCl3 lewis structure
We will see what are the characteristics of AlCl3 lewis structure.
- Each Chlorine atom has made a single bond with Aluminium atom.
- There are three lone pairs on each chlorine atom's valence shell.
Steps of drawing lewis structure of AlCl3
When we draw a lewis structure of a molecule or an ion, there are specific guidelines and steps to follow. Number of steps you need to draw the lewis structure, can be changed according the complexity of the molecule or ion. Those all steps and guidelines are mentioned and explained in detail in this tutorial for your knowledge improvement.
- Find total number of electrons of the valance shells of aluminium and chlorine atoms
- Find total number of electrons pairs existing as lone pairs and bonds
- Determine center atom
- Mark lone pairs on atoms
- Mark charges on atoms if there are.
- Check the stability and minimize charges on atoms by converting lone pairs to bonds to obtain best lewis structure.
Find total number of electrons of the valance shells of AlCl3
There are three elements in AlCl3 molecule. To determine number of electrons in valence shell of atom, you need to know that where (respective group) an element is located in the periodic table.
- Aluminium is a group IIIA element in the periodic table and contains three electrons in its last shell.
- Chlorine is located at VIIA group and has seven electrons in its valence shell.
Now, we know how many electrons are there in valence shells of aluminium and chlorine atoms. To find out total number of valence electrons given by an specific element in a molecule, you should multiply number of valence electrons by number of respective atoms in that molecule as below.
- valence electrons given by aluminium atom = 3 * 1 = 5
- valence electrons given by chlorine atom = 7 * 3 = 21
- Because, there is no overall charge in molecule, no additions or deductions to the total number of valence electrons.
- Total number of valence electrons = 3+ 21
- Total number of valence electrons = 24
Determine total valence electrons pairs
Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells
Total electron pairs are determined by dividing the number total valence electrons by two. For, aluminium chloride, total number of pairs of electrons are twelve in their valence shells.
Selection of center atom of AlCl3
Deciding the center atom is an important fact in drawing lewis structures. Having higher valence and being the most electropositive element are the main key facts of selection of center atom.
- Fact 1: Because, chlorine atom can show higher valence (7) than aluminium atom (3), chlorine atom has the higher priority to be the center atom considering fact of higher valence.
- Fact 2: But, Aluminium is more electropositive than chlorine, then aluminium atom has the higher priority to be the center atom.
- Now, there is a confusion of selecting the center atom between chlorine or aluminium.
- Fact 3: Considering the stability of phosphorus and chlorine atoms when they make covalent compounds, there should be at least three bonds around aluminium atom because aluminium's only valence is 3. But for chlorine, it is enough to have one bond because chlorine has variety of valences (1, 3, 5, 7)
- From fact 3, we can decide that, aluminium atom should be the center atom because there should be at least three bonds around aluminium atom.
- By thinking like this, we have found that following skeletal is the most suitable one to draw the most stable lewis structure of aluminium chloride.
Mark lone pairs on atoms
After determining the center atom and skeletal of AlCl3 molecule, we can start to mark lone pairs on atoms. Remember that, there are total of twelve electron pairs to mark as lone pairs and bonds.
- There are already three bonds in the above drawn skeletal. So, there are nine remaining lone pairs to mark on atoms.
- Start to mark remaining lone pairs on outside atoms (in this case: on chlorine atoms). Each chlorine atom will take three lone pairs. So nine lone pairs can be marked on three chlorine pairs. Then, no more lone pairs are remaining to mark.
Mark charges on atoms
There are no charges on atoms in the above drawn structure as below.
Check the stability and minimize charges on atoms by converting lone pairs to bonds
Because there are no charges on any atom, above structure is already stable and can confirm that this structure is the lewis structure of AlCl3.
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