Difference Between Polar and Non Polar

Polar Molecule

A polar molecule is a molecule in which one end becomes partially positive while the other end becomes partially negative. This occurs because of the unequal sharing of electrons between atoms having different electronegativities. A diatomic molecule which contains a polar covalent bond in between two hetero atoms, such as HF, is considered to be a polar molecule. The two electrically charged regions (positive and negative) on both ends of the bond of the molecule are called poles. A molecule containing two such poles is termed a dipole. Hydrogen fluoride is an example of a dipole. The formation of dipole results from an unequal distribution of electron cloud density throughout the bond between two atoms of the molecule.

Non-Polar Molecule

A non-polar molecule is a molecule in which the distribution of electric charge is uniform throughout the molecule. In such molecules, there are no positive or negative poles because the electrons are shared equally between the bonded atoms.

Non-polar molecules are generally formed when:

• Two identical atoms form a covalent bond, or
• The molecule has a symmetrical shape that cancels out the dipole moments.

Nonpolar molecules are symmetric. For example, a tetrahedral molecule such as $\mathrm{CCl}_4$ is nonpolar; boron trifluoride, $\mathrm{BF}_3$ is a trigonal planar molecule and nonpolar.

Polar Molecule Examples

• Water is a polar molecule. The bonds between hydrogen and oxygen are distributed as if the hydrogen atoms are both on each side of the oxygen atom rather than evenly placed. The oxygen contains a partial negative whereas hydrogen contains a partial positive charge.
• Ethanol is a polar molecule. The oxygen atoms of the hydroxyl group attract electrons because they are more highly electronegative than other atoms in the molecule. Thus the hydroxyl group in ethanol has a partially negative charge.
• Ammonia $\left(\mathrm{NH}_3\right)$ is a polar molecule.
• Sulfur dioxide $\left(\mathrm{SO}_2\right)$ is a polar molecule.
• Hydrogen sulfide $\left(\mathrm{H}_2 \mathrm{~S}\right)$ is a polar molecule.

In carbon dioxide, polar bonds are present but the dipole moments cancel out each other due to its linear shape. Hence, it is a nonpolar molecule.

Examples of Nonpolar Molecules

A few examples of non-polar molecules are oxygen, ozone, nitrogen, carbon dioxide, methane, gasoline,etc. Examples of homonuclear nonpolar molecules are oxygen $\left(\mathrm{O}_2\right)$, nitrogen $\left(\mathrm{N}_2\right)$, and ozone $\left(\mathrm{O}_3\right)$.

Alkynes are other examples of nonpolar molecules as they are insoluble in water.

The noble gases are also non-polar in nature.

Difference Between Polar And Non-Polar Molecules

What Is Polar and Non-polar Bond?

Nonpolar Covalent Bonds

A nonpolar covalent bond is a type of covalent bond in which the bonded atoms share electrons equally. This equal sharing occurs when the atoms have the same or nearly the same electronegativity. Since the electrons are equally distributed between the atoms, no positive or negative poles are formed. Therefore, nonpolar covalent bonds do not produce any dipole moment. Nonpolar covalent bonds are commonly formed between atoms of the same element.

Polar covalent bonds

A polar covalent bond is a type of covalent bond in which the bonded atoms share electrons unequally. This unequal sharing occurs because one atom is more electronegative than the other and attracts the shared electron pair more strongly. As a result, one atom develops a partial negative charge ( $\delta^{-}$), while the other develops a partial positive charge $\left(\delta^{+}\right)$. This creates polarity in the bond and produces a dipole moment.

In hydrogen fluoride, the electron density is unevenly distributed. Higher density is towards fluorine and lower density is towards hydrogen atom.

The atom having higher electronegativity acquires a partial negative charge whereas the atom with less electronegativity acquires a partial positive charge.

Difference Between Polar And Non-polar Bonds

Difference Between Polar And Non-Polar Solvents

Boiling Point Of Polar And Nonpolar Molecules

The existence of dipole forces explains why polar molecules have higher boiling points and melting points than nonpolar molecules. In the following table, we compare the boiling points of several pairs of molecules. In each pair, one molecule is polar and the other is nonpolar, but otherwise, they are as similar as possible. The polar substance always has a higher boiling point, indicating greater attractive forces between separate molecules, that is, larger intermolecular forces.

Also Read:

• NCERT solutions for Class 11 Chemistry Chapter 12 Organic chemistry
• NCERT Exemplar Class 11 Chemistry Solutions Chapter 12 Organic chemistry
• NCERT notes Class 11 Chemistry Chapter 12 Organic chemistry

Some Solved Examples

Example 1: Displacement of $\pi$ electron of a multiple bond towards the atom or away from the atom at the demand of reagent is called
1) (correct) Electromeric effect
2) inductive effect
3) mesomeric effect
4) hyperconjugation

Solution
As we have learned
The displacement of $\pi$ electrons in multiple bonds towards the atom or away from the atom at the demand of a reagent is called the electromeric effect.

Hence, the answer is the option (1).

Example 2: Given below are two statements:

Statement I: $\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}$ and AgCN both can generate nucleophile.
Statement II: KCN and AgCN both will generate nitrile nucleophiles with all reaction conditions.

Choose the most appropriate option:
1) Both Statement I and Statement II are true
2) Both Statement I and Statement II are false
3) (correct) Statement I is true but Statement II is false
4) Statement I is false but Statement II is true

Solution

We know the below facts -
$\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}$ and AgCN both can generate nucleophiles.
KCN and AgCN both will NOT generate nitrile nucleophiles with all reaction conditions.

So, Statement I is true but Statement II is false.

Hence, the answer is the option (3).

Example 3: The strongest acid amongst the following compounds is :

1) $\mathrm{CH}_3 \mathrm{COOH}$
2) HCOOH
3) (correct) $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}(\mathrm{Cl}) \mathrm{CO}_2 \mathrm{H}$
4) $\mathrm{ClCH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}$

Solution
$
\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}(\mathrm{Cl}) \mathrm{CO}_2 \mathrm{H}
$

$\alpha-$ chlorobutyric acid is a stronger acid than others due to the -e effect (electron-withdrawing group) of Cl.

Hence, the answer is the option (3).

Example 4: Select an incorrect statement about the Electromeric effect

1) It involves polarisation of $\pi$ electrons in the presence of a reagent
2) It is a temporary effect
3) Electrophilic reagents are generally the cause for this effect in Alkenes
4) (correct) The polarization of $\pi$ electrons persists even after the reagent has been removed from the system

Solution

The electromagnetic effect is a temporary effect in which the $\pi$ electrons are polarised in the presence of an attacking reagent.

The polarization is not present in the absence of the reagent

Hence, the answer is option(4).

Practice more question with the link given below

Also read