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BCl3 Molecular Geometry - Science Education and Tutorials

BCl3 Molecular Geometry

Boron trichloride(BCl3) has the composition of one boron and three chlorine atoms. What is the molecular geometry of boron trichloride?. Drawing and predicting the BCl3 molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct BCl3 molecular geometry. Chlorine and boron come from the 17th and 13th family groups in the periodic table. Chlorine and boron have seven and three valence electrons respectively.

Key Points To Consider When drawing The BCl3 Molecular Geometry

A three-step approach for drawing the BCl3 molecular can be used. The first step is to sketch the molecular geometry of the BCl3 molecule, to calculate the lone pairs of the electron in the central boron atom; the second step is to calculate the BCl3 hybridization, and the third step is to give perfect notation for the BCl3 molecular geometry.

The BCl3 molecular geometry is a diagram that illustrates the number of valence electrons and bond electron pairs in the BCl3 molecule in a specific geometric manner. The geometry of the BCl3 molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory) and molecular hybridization theory, which states that molecules will choose the BCl3 geometrical shape in which the electrons have from one another in the specific molecular structure.

Finally, you must add their bond polarities characteristics to compute the strength of the B-Cl bond (dipole moment properties of the BCl3 molecular geometry). The Boron-chlorine bonds in the boron trichloride(BCl3), for example, are polarised toward the more electronegative value chlorine atom, and because all (B-Cl) bonds have the same size and polarity, their sum is zero due to the BCl3 molecule’s bond dipole moment due to it oppose to each other in the trigonal planar geometry, and the BCl3 molecule is classified as a nonpolar molecule.

BCl3 Molecular Geometry

The molecule of boron trichloride (with trigonal planar shape BCl3 molecular geometry) is tilted at 120 degrees bond angle of Cl-B-Cl. It has a difference in electronegativity values between boron and chlorine atoms, with chlorine’s pull the electron cloud being greater than boron’s. But bond polarity of B-Cl canceled to each other in the trigonal planar geometry. As a result, it has no permanent dipole moment in its molecular structure. The BCl3 molecule has no dipole moment due to an equal charge distribution of negative and positive charges.

Overview: BCl3 electron and molecular geometry

According to the VSEPR theory, BCl3 possesses trigonal planar molecular geometry. Because the center atom, boron, has three B-Cl bonds with the chlorine atoms surrounding it. The Cl-B-Cl bond angle is 120 degrees in the trigonal planar molecular geometry. The BCl3 molecule has a trigonal planar geometry shape because it contains three chlorine atoms.

There are three B-Cl bonds at the BCl3 molecular geometry. After linking the three chlorine atoms and no lone pairs of electrons in the trigonal planar form, it maintains the planar-T-like structure. In the BCl3 molecular geometry, the B-Cl bonds have stayed in the three terminals and no lone pairs of electrons in the top and bottom of the trigonal planar molecule.

The center boron atom of BCl3 has no lone pairs of electrons, resulting in trigonal planar electron geometry. However, the molecular geometry of BCl3 looks like a trigonal planar and no lone pairs on the top and bottom of the BCl3 geometry. It’s the BCl3 molecule’s symmetrical geometry. As a result, the BCl3 molecule is nonpolar.

How to find BCl3 hybridization and molecular geometry

Calculating lone pairs of electrons on boron in the BCl3 geometry:

1.Determine the number of lone pairs on the core boron atom of the BCl3 Lewis structure. Because the lone pairs on boron are mostly responsible for the BCl3 molecule geometry distortion, we need to calculate out how many there are on the central boron atom of the Lewis structure.

Use the formula below to find the lone pair on the boron atom of the BCl3 molecule.

L.P(B) = V.E(B) – N.A(B-Cl)/2


Lone pair on the central boron atom = L.P(B)

The core central boron atom’s valence electron = V.E(B)

Number of B-Cl bonds = N.A (B-Cl)

calculation for boron atom lone pair in BCl3 molecule

For instance of BCl3, the central atom, boron, has three electrons in its outermost valence shell, three B-Cl bond connections.

As a result of this, L.P(B) = (3 –3)/2=0

In the BCl3 electron geometry structure, the lone pair on the central boron atom is zero. It means there are no lone pairs of electrons in the core boron atom. This makes BCl3 molecule electron deficient. It makes coordination with ammonia. No lone pairs of electrons on the central boron atom are responsible for the planar nature of BCl3 molecular geometry.

If you imagine, there is no lone pair on the boron atom of the BCl3 molecule. Then, electronic repulsion of B-Cl bonds pair and zero lone pair of electrons in the BCl3. That gives stable trigonal planar geometry. No lone pairs of electrons are located on the top and bottom of the geometry. It makes a stable trigonal planar structure.

But in reality, the BCl3 molecule undergoes distortion in its geometry due to the polarity of the B-Cl bond and no lone pairs of electrons in the trigonal planar geometry. This leads to a trigonal planar for the BCl3 molecule.

Calculate the number of molecular hybridizations of the BCl3 molecule

What is BCl3 hybridization? This is a very fundamental question in the field of molecular chemistry. All the molecules made by atoms. In chemistry, atoms are the fundamental particles. There are four different types of orbitals in chemistry. They are named as s, p, d, and f orbitals.

The entire periodic table arrangement is based on these orbital theories. Atoms in the periodic table are classified as follows:

s- block elements

p- block elements

d-block elements

f-block elements

Atoms are classified in the periodic table

BCl3 molecule is made of one boron and three chlorine atoms. The boron atom has s and p orbitals. Chlorine comes as the second element from the halogen family in the periodic table. The chlorine atom has s and p orbitals.

When these atoms combine to form the BCl3 molecule, its atomic orbitals mixed and form unique molecular orbitals due to hybridization.

How do you find the BCl3 molecule’s hybridization? We must now determine the molecular hybridization number of BCl3.

The formula of BCl3 molecular hybridization is as follows:

No. Hyb of BCl3= N.A(B-Cl bonds) + L.P(B)

No. Hy of BCl3= the number of hybridizations of BCl3

Number of B-Cl bonds = N.A (B-Cl bonds)

Lone pair on the central boron atom = L.P(B)

Calculation for hybridization number for BCl3 molecule

In the BCl3 molecule, the boron is a core central atom with three chlorine atoms connected to it and no lone pairs of electrons. The number of BCl3 hybridizations (No. Hyb of BCl3) can then be estimated using the formula below.

No. Hyb of BCl3= 3+0 =3

The BCl3 molecule hybridization is three. The boron atom has s and p orbitals. The chlorine atom has s and p orbital. The sp2 hybridization of the BCl3 molecule is formed when one S orbital and two p orbitals join together to form a molecular orbital.

Molecular Geometry Notation for BCl3 Molecule :

Determine the form of BCl3 molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the BCl3 molecule.

The AXN notation of BCl3 molecule is as follows:

The center boron atom in the BCl3 molecule is denoted by the letter A.

The bound pairs (three B-Cl bonds) of electrons to the core boron atom are represented by X.

The lone pairs of electrons on the central boron atom are denoted by the letter N.

Notation for BCl3 molecular geometry

We know that boron is the core atom, with three electron pairs bound (three B-Cl) and zero lone pair of electrons. The general molecular geometry formula for BCl3 is AX3.

According to the VSEPR theory, if the BCl3 molecule has an AX3 generic formula, the molecular geometry and electron geometry will both be trigonal planar forms.

Name of MoleculeBoron trichloride
Chemical molecular formulaBCl3
Molecular geometry of BCl3Trigonal planar
Electron geometry of BCl3Trigonal planar
Hybridization of BCl3sp2
Bond angle (Cl-B-Cl)120º degree
Total Valence electron for BCl324
The formal charge of BCl3 on boron0

Summary:

In this post, we discussed the method to construct BCl3 molecular geometry, the method to find the lone pairs of electrons in the central boron atom, BCl3 hybridization, and BCl3 molecular notation. Need to remember that, if you follow the above-said method, you can construct the BCl3 molecular structure very easily.

What is BCl3 Molecular geometry?

BCl3 Molecular geometry is electronic structural representation of molecule.

What is the molecular notation for BCl3 molecule?

BCl3 molecular notation is AX3.

The polarity of the molecules

The polarity of the molecules are listed as follows

Lewis Structure and Molecular Geometry

Lewis structure and molecular geometry of molecules are listed below

External References

Information on boron trichloride(BCl3) molecule

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