CS2 is the chemical formula for the carbon disulfide molecule. It is a poisonous, flammable, and volatile liquid. CS2 has a molar mass of 76.139 g/mol. It is frequently used as a building block in organic chemistry, as well as an industrial and chemical non-polar solvent.
Does the above statement give you a hint about the polarity of the carbon disulfide (CS2) molecule?
If yes, then you guessed it right, and if you didn’t, no worries, we will lead you through the article. Either way, continue reading to find out the correct answer and its explanation!
Is CS2 polar or non-polar?
Carbon disulfide (CS2) is a non-polar molecule. CS2 consists of a carbon (C) atom and two sulfur (S) atoms. The carbon atom is present at the center of the molecule, while both sulfur atoms occupy terminal positions, one on each side, making a linear molecular shape and geometry.
A slight electronegativity difference of 0.03 units exists between a carbon and a sulfur atom in each C=S bond in the CS2 molecule. Thus, the two covalent bonds are only weakly polar in the CS2 molecule with a very small dipole moment value (symbol µ).
However, it is due to the symmetrical linear shape of CS2 that the small dipole moment of C=S bonds cancels out each other equally. The electron cloud stays uniformly distributed in the molecule overall. Thus, CS2 is a non-polar molecule (net µ = 0).
A molecule is polar if there is a non-uniform charge distribution present in it. If the charge distribution gets equally balanced in different parts, then that molecule or molecular ion is considered non-polar.
The following three factors mainly influence the polarity of a molecule:
The electronegativity difference between two or more covalently bonded atoms
Dipole moment
Molecular geometry or shape
Now, let us discuss the effect of the above three factors one by one to prove that the carbon disulfide CS2 is overall a non-polar molecule.
Factors affecting the polarity of CS2
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 bonded atoms in a molecule, the higher the bond polarity.
Carbon (C) is present in Group IV A (or 14) of the Periodic Table. The electronic configuration of carbon is 1s2 2s2 2p2. As per this electronic configuration, a C-atom has a total of 4 valence electrons. It is thus short of 4 more electrons that are required so that the carbon atom can achieve a complete octet electronic configuration.
Conversely, Sulfur (S) belongs to Group VI-A (or 16) of the Periodic Table. The electronic configuration of a sulfur atom is 1s2 2s2 2p6 3s2 3p4. Hence, each S-atom in CS2 has a deficiency of 2 more valence electrons to achieve a stable octet.
Hence in the CS2 molecule, each of the two S-atoms is double-covalently bonded to the central C-atom. No lone pairs of electrons are present on the central C-atom, while each S-atom contains two lone pairs of electrons.
In this way, all three bonded atoms attain a complete octet electronic configuration via chemical bonding in the CS2 molecule.
Due to the absence of any lone pair of electrons on the central carbon (C) atom, there is no distortion in the shape of the molecule and the CS2 molecule attains a linear molecular shape.
Atom
Electronic configuration
Valence electrons
Carbon (6C)
1s2 2s2 2p2
4
Sulfur (16S)
1s2 2s2 2p6 3s2 3p4
6
The electronegativity of carbon is 2.55, and sulfur is 2.58. Thus, the electronegativity difference between the bonded carbon and sulfur atoms is 0.03 units in each C=S bond in the CS2 molecule.
It is due to this small electronegativity difference between carbon and sulfur atoms that each C=S bond is only weakly polar.
The terminal S-atoms attract the shared C=S electron cloud to a small extent and obtain partial negative (δ–) charges. Contrarily, the central C-atom gains a partial positive charge (δ+) due to a slight electron deficiency, as shown in the figure below.
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 a polar covalent bond conventionally points from the positive center to the center of the negative charge.
So in CS2, each C=S bond has a small dipole moment value. The dipole moment points from Cδ+ to Sδ- (as shown below).
Molecular geometry
According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, CS2 is an AX2E0 or simply AX2– type molecule. To one C-atom at the center (A), two C=S bond pairs (X) are attached, and there is no lone pair (E) on the central atom.
So, the molecular geometry or shape of CS2 is identical to its ideal electron pair geometry, i.e., linear. Due to the absence of any lone pair of electrons on the central C-atom, the molecule gets influenced to adopt a symmetrical shape, and it attains a linear molecular shape with an ideal 180° bond angle.
It is due to the symmetrical shape that the dipole moment generated on both sides along each C=S bond cancels out each other making it a non-polar molecule. Thus, carbon disulfide CS2 is overall non-polar (net µ = 0).
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), nitrogen trichloride (NCl3), nitrogen trifluoride (NF3), etc.
Examples include oxygen (O2), nitrogen (N2), methane (CH4), carbon disulfide (CS2), etc.
CS2 has slightly polar bonds due to a small electronegativity difference of 0.03 units between the bonded carbon (E. N= 2.55) and sulfur (E. N= 2.58) atoms in each of the two C=S bonds.
However, the CS2 molecule attains a symmetrical linear shape. Due to this arranged symmetry, the molecule has an equal distribution of charge. The dipole moment generated on both sides along the C=S bonds cancels out each other, making it a non-polar molecule.
Consequently, the carbon disulfide CS2 molecule s overall non-polar with a net dipole momentµ = 0.
According to VSEPR theory, what is the shape of the CS2 molecule?
According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, CS2 is an AX2E0 -type molecule.
To one C-atom at the center (A), two C=S bond pairs (X) are attached, and there is no lone pair (E) on the central atom.
As a result, CS2 attains a linear molecular shape, identical to its ideal electron pair geometry.
Why CS2 has zero dipole moment?
CS2 contains two C=S bonds that are arranged symmetrically. Due to this, the dipole moment generated on both sides along the C=S bond cancels out each other’s effect completely (net µ = 0), making it a non-polar molecule.
Why CS2 molecule and HgCl2 are linear and non-polar?
In both CS2 and HgCl2, the central atom is attached to only two other atoms, and there is no lone pair of electrons on the central atom. Thus there are no lone pair-lone pair or lone pair-bond pair repulsions present in the molecules, resulting in a symmetrical linear shape.
Each C=S bond is only weakly polar in the CS2 molecule due to an electronegativity difference of 0.03 units between the bonded atoms. The small C=S dipole moments get canceled equally on each side of the molecule; thus, it is overall non-polar.
Contrarily, there is a much higher (1.16 units) electronegativity difference between the bonded atoms in each Hg-Cl bond in HgCl Still, its linear shape results in a complete dipole moment cancellation; thus, it is also non-polar.
Which of the following molecules are non-polar, and which ones are polar?
PF3
CS2
SF4
SF6
Carbon disulfide (CS2) and sulfur hexafluoride (SF6) are non-polar molecules, while phosphorus trifluoride (PF3) and sulfur tetrafluoride (SF4) are polar molecules.
The small dipole moments of C=S bonds get canceled equally in the linear shape of CS2; thus, it is non-polar (net µ = 0).
The dipole moments of S-F bonds get canceled equally in the octahedral shape and molecular geometry of SF6. The charged electron cloud stays uniformly distributed over the molecule; thus, it is also non-polar (net µ = 0).
Zero formal charges are present on each S-atom and on the central C-atom; thus, the overall charge present on the carbon disulfide molecule is (0) + (0) = 0.
Summary
Carbon disulfide (CS2) is a non-polar molecule.
It consists of two C=S weakly polar bonds due to an electronegativity difference of 0.03 units between a carbon and a sulfur atom.
Carbon disulfide CS2 has a symmetrical linear shape with a 180° S=C=S bond angle.
The electron cloud stays uniformly distributed in the symmetrical CS2 linear molecular shape.
Due to the absence of any lone pair of electrons on the central C-atom, the dipole moment of both weakly polar C=S bonds gets canceled out (net µ = 0).
The net dipole moment in CS2 is zero, so it is overall non-polar.
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