Beryllium chloride is a colorless or yellowish hexagonal crystalline solid represented by the chemical formula BeCl2. It is a hygroscopic compound with a sharp odor and is miscible with many polar solvents.
BeCl2 is chiefly employed as a raw material in electrochemical industries and as a catalyst for many organic reactions.
Many students have doubts about the polarity of beryllium chloride (BeCl2). So, is BeCl2 polar or non-polar? Continue reading to find out.
Is BeCl2 polar or non-polar?
Beryllium chloride (BeCl2) is a non-polar molecule, However, each Be-Cl bond in the BeCl2 molecule is polar due to an electronegativity difference between the bonded Be and Cl atoms.
The electronegativity of the chlorine (Cl) atom is greater than the beryllium (Be) atom. The Cl atom strongly attracts the shared electron pair in the Be-Cl bond.
Thus, each Be-Cl bond in the BeCl2 molecule is polar and possesses a dipole moment value.
However, the individual Be-Cl dipole moments get canceled in the symmetric, linear BeCl2 molecule. Thus, BeCl2 is a non-polar molecule with a net dipole moment equal to 0.
In chemistry, a molecule with unequal charge distribution between different centers of bonded atoms is a polar molecule.
It is formed by the covalent bond between two different atoms leading to an asymmetric electron density.
In this case, the atoms acquire partial positive (δ+) and partial negative (δ–) charges.
In the case of symmetric molecules, If the dipole moments of individually polar bonds are canceled, the molecule will be non-polar, such as BeCl2.
Hence a polar molecule has an unequal distribution of the electronic charge. Contrarily, if the electronic charge is evenly distributed over the molecule, in that case, it will be a non-polar molecule overall.
The following three factors influence the polarity of any covalent molecule:
Electronegativity.
Dipole moment.
Molecular geometry or shape.
How do these factors lead to the non-polar nature of the BeCl2 molecule? Continue reading to find out.
Factors affecting the polarity of BeCl2
Electronegativity
It is defined as the ability of an atom to attract a shared pair of electrons from a covalent chemical bond.
Electronegativity decreases down the group in the Periodic Table of elements while it increases across a period.
Greater the electronegativity difference between the bonded atoms in a molecule, the higher the bond polarity.
Chlorine belongs to group VII-A (or 17) of the Periodic Table. The electronic configuration of chlorine is 1s22s22p6 3s2 3p5, so it has 7 valence electrons for bonding.
On the other hand, beryllium belongs to group II-A (or 2A) of the Periodic Table. The electronic configuration of beryllium is 1s22s2, so it has 2 valence electrons. The two Cl atoms thus form single covalent bonds with the central Be-atom to complete their stable valence shell configuration.
One valence electron consumed in bonding out of the seven initially available leaves behind six valence electrons, i.e., three lone pairs of electrons on each Cl atom in the BeCl2 molecule.
Atom
Electronic configuration
Valence electrons
Beryllium (4Be)
1s22s2
2
Chlorine (17Cl)
1s22s22p6 3s2 3p5
7
Chlorine (E.N = 3.16) is more electronegative than beryllium (E.N = 1.57). An electronegativity difference of 1.59 units is present between these two bonded atoms.
Due to this electronegativity difference, chlorine strongly attracts the shared electron cloud from the Be-Cl bond in the BeCl2 molecule. The bonded electrons are held significantly close to the chlorine.
The Cl-atom thus gains a partial negative (Clδ-) charge, while the beryllium atom, less electronegative, obtains a partial positive (Beδ+) charge. In this way, oppositely charged poles develop in the BeCl2 molecule.
Consequently, each Be-Cl bond in the BeCl2 molecule is polar. This is called the bond polarity of BeCl2.
Dipole Moment
The dipole moment is the product of electrical charge (Q) and bond length (r) between two bonded atoms. It is a vector quantity expressed in Debye (D) units.
It is represented by a Greek symbol µ and measures the polarity of a bond.
The dipole moment of any molecule depends on the difference in electronegativity between the bonded atoms. The greater the electronegativity difference, the higher the bond polarity, resulting in a high dipole moment value.
It points from the partial positive (δ+) center to the partial negative (δ–) center of a bond or molecule.
As each Be-Cl bond in the BeCl2 molecule is polar, both have a specific dipole moment value.
The dipole moment of each Be-Cl bond points from the Beδ+ to Clδ-.
Molecular geometry
As discussed earlier, a beryllium chloride (BeCl2) molecule consists of two single Be-Cl covalent bonds. The overall molecule consists of a total of 16 valence electrons.
According to the Valence Shell Electron Pair Repulsion Theory (VSEPR) theory of chemical bonding, BeCl2 is an AX2-type molecule. Two bond pairs are attached to one atom of beryllium in the center, and there are no lone pairs on the central atom.
Due to the absence of disorientation due to no lone pairs on the central Be-atom, the BeCl2 molecule has a linear shape with a mutual bond angle of 180°.
As a result, the dipole moment generated on both sides along the Be-Cl bond will cancel out each other, making it a non-polar molecule.
In conclusion, BeCl2 is a non-polar molecule with a net dipole moment value equal to zero.
Difference between polar and nonpolar?
Polar molecule
Non-polar molecule
Atoms must have a difference in
electronegativity
Atoms may have the same or different electronegativity values
Unequal charge distribution overall
Equal charge distribution overall
Net dipole moment greater than zero
Net dipole moment equals to zero
Examples include water (H2O), ethanol (CH3CH2OH), ammonia (NH3), sulfur dioxide (SO2), bromine trifluoride (BrF3), nitric oxide (NO), bromine pentafluoride (BrF5), etc.
Examples include oxygen (O2), nitrogen (N2), methane (CH4), carbon disulfide (CS2), beryllium chloride (BeCl2), etc.
Why is beryllium chloride (BeCl2) a non-polar molecule even though it has polar bonds?
The individual Be-Cl bonds in the BeCl2 molecule are polar due to a great electronegativity difference between Be and Cl atoms.
But the molecule (BeCl2) overall is non-polar because it has a symmetric linear geometry.
The individual dipole moments get canceled in opposite directions. So-net dipole moment µ becomes zero in the molecule.
Thus, BeCl2 is a non-polar molecule with a zero net dipole moment.
BeCl2 is non-polar, and H2O is polar, but BeCl2 dissolves in H2O. How is this possible?
BeCl2 is a non-polar molecule, but it has polar Be-Cl bonds. It uses these polar Clδ- ends and the Beδ+ center to interact with and dissolve in polar solvents such as water (H2O).
Which among the following is a polar molecule CH4, BF3, IF3, and BeCl2?
Out of all these, only IF3 is a polar molecule. All the other three molecules are non-polar in nature.
IF3 has three bond pairs and two lone pairs on iodine. IF3 forms an asymmetric T shape. The dipole moment effect of individual I-F bonds is not completely canceled.
So, IF3 is a polar molecule with a net dipole moment µ value of 0.63 D.
The individual dipole moments in the linear BeCl2 molecule get canceled in opposite directions, so net µ becomes zero in the molecule. Thus, BeCl2 is non-polar.
Is there a formal charge on the bonded atoms in the BeCl2 molecule?
Formal charge of an atom = [ valence electrons – non-bonding electrons- ½ (bonding electrons)]
For chlorine atoms
Valence electrons = 7
Bonding electrons = 2
Non-bonding electrons = 6
∴ The formal charge on the chlorine atoms = 7-6-2/2 = 1-1 = 0
For beryllium atom
Valence electrons = 2
Bonding electrons = 4
Non-bonding electrons = 0
∴ The formal charge on the beryllium atom = 2-0-4/2 = 1-1 = 0
Thus, no formal charge is present on the beryllium chloride (BeCl2) molecule.
Summary
Beryllium chloride (BeCl2) is a non-polar molecule.
The individual Be-Cl bonds are polar due to an electronegativity difference of 1.59 units between the bonded atoms.
The difference in electronegativity between the bonded atoms leads to the formation of dipoles pointing from Beδ+ to Clδ-.
Due to the symmetric linear molecular geometry of BeCl2, the individual Be-Cl dipole moments get canceled in opposite directions.
In conclusion, BeCl2 is a non-polar molecule with net µ =0.
The Cl-Be-Cl bond angle is 180°.
All the Be-Cl bonds are equivalent in the linear structure of BeCl2, so each Be-Cl bond length is 181.4 pm.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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