The Lewis structure of BCl3 contains three single bonds, with boron in the center, and three chlorines on either side. There are three lone pairs on each chlorine atom, and the boron atom does not have any lone pair.
Steps
By using the following steps, you can easily draw the Lewis structure of BCl3:
#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)
Let’s one by one discuss each step in detail.
#1 Draw skeleton
In this step, first calculate the total number of valence electrons. And then, decide the central atom.
- Let’s calculate the total number of valence electrons
We know that… boron is a group 13 element and chlorine is a group 17 element. Hence, boron has three valence electrons and chlorine has seven valence electrons.
Now BCl3 has one boron atom and three chlorine atoms.
So the total number of valence electrons = valence electrons of boron atom + (valence electrons of chlorine atom × 3)
Therefore, the total number of valence electrons = 3 + 21 = 24
- Now decide the central atom
The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for boron and chlorine as follows:
Electronegativity value of boron = 2.04
Electronegativity value of chlorine = 3.16
Obviously, boron is less electronegative than chlorine. Hence, assume that boron is the central atom.
So now, put boron in the center and chlorines on either side. And draw the rough skeleton structure for the Lewis structure of BCl3 something like this:
Also read: How to draw Lewis structure of CN– (5 steps)
#2 Show chemical bond
Place two electrons between the atoms to show a chemical bond. Since boron is surrounded by three chlorines, use six electrons to show three chemical bonds as follows:
Also read: How to draw Lewis structure of CF4 (4 steps)
#3 Mark lone pairs
As calculated earlier, we have a total of 24 valence electrons. And in the above structure, we have already used six valence electrons. Hence, eighteen valence electrons are remaining.
Two valence electrons represent one lone pair. So eighteen valence electrons = nine lone pairs.
Note that boron is a period 2 element, so it can not keep more than 8 electrons in its last shell. And chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.
Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.
The outside atoms are chlorines, so each chlorine will get three lone pairs. And the central atom (boron) will not get any lone pair, because all nine lone pairs are used.
So the Lewis structure of BCl3 looks something like this:
In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (boron) doesn’t form an octet.
Now boron has an exception in BCl3, that it does not require eight electrons to complete its octet.
So one last thing we need to do is, calculate the formal charge and check the stability of the above structure.
Also read: How to draw Lewis structure of PF3 (4 steps)
#4 Calculate formal charge and check stability
The following formula is used to calculate the formal charges on atoms:
Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons
Collect the data from the above structure and then, write it down below as follows:
- For boron atom
Valence electrons = 3
Nonbonding electrons = 0
Bonding electrons = 6
Formal charge = 3 – 0 – ½ (6) = 0
- For each chlorine atom
Valence electrons = 7
Nonbonding electrons = 6
Bonding electrons = 2
Formal charge = 7 – 6 – ½ (2) = 0
Mention the formal charges of atoms on the structure. So the Lewis structure of BCl3 looks something like this:
In the above structure, you can see that the formal charges of both (boron and chlorine) are zero. Therefore, this is the stable Lewis structure of BCl3.
And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.
Related
- Lewis structure of CN–
- Lewis structure of CF4
- Lewis structure of PF3
- Lewis structure of XeF4
- Lewis structure of F2
External links
- Lewis Structure of BCl3, Boron Trichloride (and Hybridization) – ChemistNate
- BCl3 Lewis Structure in 5 Steps (With Images) – Pediabay
- BCl3 lewis structure, molecular geometry, bond angle, hybridization – Topblogtenz
- BCl3 Lewis Structure, Molecular Geometry, Hybridization and Shape – Geometry of Molecules
- BCl3 Lewis Structure, Molecular Geometry, and Hybridization – Techiescientist
- What is the structure of BCl3? – Quora
- Draw the Lewis structure for BCl3 – Homework.Study.com
- Chemical Bonding: BCl3 Lewis Structure – The Geoexchange
- How to draw BCl3 Lewis Structure? – Science Education and Tutorials
- Boron Trichloride, BCl3 Molecular Geometry & Polarity – Tutor-Homework.com
- How to Draw the Lewis Structure for BCl3 – Pinterest
- Lewis structure of BCl3 – AceOrganicChem
- Lewis Dot of Boron Trichloride BCl3 – Kent’s Chemistry
- What is the molecular geometry of BCl3? Draw its VSEPR and Lewis structure – Socratic
- Draw the Lewis structure for BCl3. How many single bonds, double bonds, triple bonds, and unshared pairs of electrons are on the central atom, in that order – Brainly
Deep
Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.