Difference Between Polar and Non Polar

The polarity of a bond is decided mainly by electronegativity. The higher the difference between the electronegativity of atoms forming a bond, the higher will be the polarity of that bond. On the basis of the polarity of bonds, we can categorize the compounds mainly in two categories, i.e. Polar compounds and Nonpolar compounds. The solubility of compounds is decided by the polarity of solute and solvent. Polarity also describes the symmetric and asymmetric nature of compounds. In this article, we will study the nature, types, and properties of various kinds of bonds based on bond polarity.

Polar and Nonpolar substance

What is Polarity?

"A state or a condition of an atom or a molecule having positive and also negative charges, especially in case of magnetic or an electrical pole."

How to identify polar and nonpolar molecules?

One can predict if a molecule is polar or nonpolar by observing the type of chemical bonds are formed in between the atoms of an elements. If there is a significant difference in between the electronegativity of the bonded atoms, the electron cloud won't be shared equally throughout the bond formed by the atoms. The atom that is more prone towards electrons will have a partial negative charge, while the atom that is less electronegative (i.e., more electropositive) will have a partial positive charge.

Polarity can be simply predicted by considering the Lewis dot structure of the molecule. If the dipole moments (due to the electronegativity of an atom) of a molecule cancel each other out, the molecule is considered to be nonpolar, whereas If the dipole moments don't cancel out each other, the molecule is considered to be polar. Every molecule doesn't possess a dipole moment. For example, a molecule that has a mirror plane won't possess a dipole moment as the individual dipole moments can't lie in more than one dimension.

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What is polar nonpolar?

Polar substances

A polar molecule is a molecule when one end of the molecule is partially positive, while the other end is partially negative. 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.

The Polar molecules, usually, orient themselves in the presence of an electric field, such that, the positive ends of the molecules are attracted to the negative plate whereas, the negative ends of the molecules are attracted to the positive plate.

In the absence of an applied electric field Polar molecules remain randomly oriented. In the presence of an electric field, the molecules orient themselves because of the attraction of opposite charges.

Non-polar substances

A molecule in which electrons are magnificently distributed does not have the charge difference present at the end. As a result, the symmetrically distributed charges cancel each other out. They are called the non-polar molecules. A solution of a polar molecule cannot be mixed with a non-polar molecule ("like dissolve like"). For example, water and oil. Here, water is referred to as a polar molecule, and oil is referred to as a nonpolar molecule. Water and oil are immiscible and thus do not form solutions.

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 and nonpolar molecules examples (list of polar molecules and non-polar molecules)

A molecule may be considered as polar or nonpolar on the basis of a few criteria. A nonpolar molecule has a linear structure such that the orbital electrons in the outer region can cancel out the net electronegativity.

• In general, pyramid-shaped and V-shaped molecules are considered to be polar. Whereas the Linear molecules are usually non-polar in nature.
• Water is said to be a polar molecule because of the high electronegativity difference between the oxygen atom and the hydrogen. Oxygen is a highly electronegative atom when compared to hydrogen.

• Examples of non-polar molecules are fats, gasoline, oil, and petrol. They are not soluble in a polar medium like water as nonpolar molecules are insoluble in water.

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

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 nonpolar compounds

What is polar and nonpolar bond (polar and nonpolar bonds)

Nonpolar Covalent Bonds

In covalent bonds, the electronegativity difference is less than 1.7. In nonpolar covalent bond bonding electrons are shared equally among the two electrons.

In a chlorine molecule, the two chlorine atoms share an electron pair in a single covalent bond and the chlorine molecule is symmetrical as it is surrounded by electron density. In a molecule when the electronegativity difference is less than 0.4 is referred to as a nonpolar covalent bond. Example: bonding between chlorine and bromine.

$(\Delta E N=3.0-2.8=0.2)$

Polar covalent bonds

In polar covalent bond electronegativity, the difference between the atoms varies between 0.4 and 1.7.

In polar covalent bonds unequal attraction of electrons is seen. The distribution of electrons surrounding the molecule is not symmetrical.

In polar covalent bond, the Greek letter delta ( $\delta$ ) is used to show uneven electron distribution.

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.

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Difference between polar and nonpolar bonds

Difference between polar and non-polar solvents

What are polar and nonpolar solvents?

Polar solvents include bonds between atoms with highly differing electronegativities, such as oxygen and hydrogen, and have significant dipole moments (also known as "partial charges"). Bonds between atoms with comparable electronegativities, such as carbon and hydrogen, exist in non-polar fluids.

The 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.

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 the option(4).

Conclusion

This article explains the difference between polar and nonpolar molecules. The nature of the bond between two atoms depends upon the difference of electronegativity. No bond is purely a covalent or ionic bond. However, it is considered that if the difference in electronegativity of atoms forming any bond is more than 1.8, then the bond is considered to be an ionic bond. The nonpolar bond forms by sharing the electron pairs equally with the bonding atoms. The polarity of compounds explains why benzene is not soluble in water. Other practical uses of polarity include understanding concepts like wetting, dispersibility, emulsification, etc.

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