Content Curator
Polar bond has an uneven distribution of the electrons between two bonded atoms, whereas a non-polar bond has an equal distribution of electrons. Molecules are formed when atoms of distinct or similar elements combine together and the bond formed by sharing a pair of electrons between two atoms is called a Covalent Bond. Covalent bonds between the atoms are classified into polar and non-polar depending on how the shared electrons are distributed between the elements that they are binding together.
Read More: Planck's Quantum Theory and Black Body Radiation
Key Terms: Bonding, Covalent Bond, Electronegativity, Atom, Molecule, Electrons, Dipole Moment, Solvents
What is a Polar Bond?
[Click Here for Sample Questions]
A polar bond is a one of the types of covalent bond. A bond between two or more atoms is polar if the atoms have a significantly different electronegativity greater than 0.4 and less than 1.8. Polar bonds do not share the electrons equally, which means the negative charge from the electrons is not evenly distributed in the molecule. This will lead to the dipole moment. The dipole moment occurs when one end of the bond is positive, and the other end is negative.
Read More: Organometallic compounds
Example for Polar Bond
The water bond between hydrogen and oxygen is the classical example for the Polar bond. This bond is classified as a polar bond because it has a large electronegativity difference of 1.4. The electrons in hydrogen atom are more attracted to the electrons in oxygen atom because the oxygen atom is more electronegative.
Polar Bond
What is a Non-Polar Bond?
[Click Here for Sample Questions]
Non-polar bonds are another type of covalent bond. Unlike polar bonds, non-polar bonds share the electrons equally. A bond between two or more atoms is said to be non-polar if the atoms have the same electronegativity or a difference in electronegativities must be less than 0.4.
Read Also: Chemical Bonding and Molecular Structure
Example for Non-Polar Bond
An example of a non-polar bond is chlorine bond. Chlorine contains only two chlorine atoms. The electrons are shared equally because the electronegativity difference between the both atoms is zero.
Non- Polar Bond
Identification of Polar and Non-Polar Bond
[Click Here for Sample Questions]
The below points are used to identify the bonds in terms of electronegativity
- When the difference in electronegativity of molecules is less than 0.4, the bond formed will be nonpolar covalent bonds.
- When the difference in electronegativity of molecules is ranging from 0.4 to 1.8, the bond formed will be polar covalent bonds.
- When the difference in electronegativity of molecules is greater than 1.8, the bond formed will be ionic bonds.
Read More: Important Notes on Carbon and its compounds
Difference between Polar and Non-Polar Bond
[Click Here for Sample Questions]
Key difference between Polar and Non-Polar Bond are:
| Parameters | Polar | Non-Polar |
|---|---|---|
| Stability | Less | More |
| Sharing of electrons | Unequal | Equal |
| Polarity | Present | Absent |
| Vapour Pressure | Low | High |
| Charge separation | Present | Absent |
| Dipole moment | Present | Absent |
| Size of Atom | Different | Equal |
| Surface Tension | High | Low |
| Example | Water | Hydrogen |
Read More: Applications of Thermal Conductivity
What are Polar and Non-Polar Solvents?
[Click Here for Sample Questions]
Polar solvents are the liquids that can dissolved in a wide range of polar compounds. This is due to the fact that polar compounds liquefy into polar solvents because the positively charged molecule of a substance is quickly attracted by the negatively charged molecule of a solvent.
Non-Polar solvents are those liquids that have zero dipole moment. These non-polar liquids do not contain any partial positive or negative charges. Non-polar solvents are unable to dissolve the polar molecules because they lack the opposing charges necessary to attract them.
Read Also: Physical Properties of Metals and Non-Metals
Things to Remember
- The nature of the shared electron movement between the different atoms is directly determined by whether the bond is polar or non-polar,
- Thus, it contributes to defining the nature of the final molecule's electrical charge.
- Non-polar bonds join two elements of equal or very similar electronegativity and are thus characterised by a very even distribution of electrons around the nuclei of the two atoms.
- The explanation about polar and non-polar molecule
- Explained the Identification of the polar and non-polar bond
- Thus, characterised by a very even distribution of electrons around the nuclei of the two atoms.
Read More: Relation Between Celsius and Fahrenheit
Sample Questions
Ques. Whether water is a covalent compound? If yes then how it is partially dissociated to form hydroxide and hydrogen ions? (3 marks)
Ans. Yes, Water is also a polar compound. It forms a polar covalent bond. The covalent compounds are said to be polar only when the shared pair of electrons are not at equal distance between the two atoms. This will result in the formation of fractional positive and negative charges on them. There will be electronegativity difference between the bonded atoms in water molecule. Due to difference in electronegativity, water dissociates into hydrogen ion and hydroxide ion.
Ques. What is meant by polar covalent compound? (3 marks)
Ans. The Polar covalent compound are the compounds which are formed between dissimilar atoms, whose electronegativity difference is greater than zero but not high. Due to the electronegativity difference, the shared pair between these atoms is been shifted towards the more electronegative atom, thereby developing a partial negative charge (-δ) on the more electronegative atom and partial positive charge (+δ) on the less electronegative atom. Hence the bond becomes polar bond, and such compounds are said to be as polar covalent compounds.
Ques. Why hydrogen peroxide is to be a polar molecule? (3 marks)
Ans. Hydrogen peroxide is a polar molecule with a bent structure. Two comparable core atoms with two unshared pair of electrons and two single bonds form an angled bond, giving the H2O2 molecule its bent shape. Dipoles do not cancel each other out since atoms do not reside in the same plane. As a result, hydrogen peroxide is classified as a polar molecule.
Ques. Are polar covalent compounds good conductors of electricity? Why? (2 marks)
Ans. Polar covalent compounds will not be able to conduct electricity. But, when they are made to dissolve in water, then they are capable of conducting electricity, as the electrons will be free to conduct electricity.
Ques. Give example for polar and non-polar molecule? (01 marks)
Ans. Examples of polar molecules are HCl, H2O, NH3, and that of non-polar molecules are H2, O2, Cl2
Ques. Methane molecule is non-polar molecule. Explain? (2 marks)
Ans. Methane is non-polar molecule because of its symmetrical tetrahedral structure. C−H bond is slightly polar but as a molecule it is non-polar because of symmetry.
Ques. Identify the non-polar molecule in the set of compounds given (1 marks)
(a)H2
(b)HCl
(c)HF, HBr
(d)HBr
Ans. Correct option is (A)
Polarity is created due to the difference in electronegativity of both atom in a molecule except H2 all other molecule has the different atom so they will have the polarity while H2 will be non-polar.
Ques. Identify each of the following compounds either as polar or non-polar molecules.
Compounds: NH3, CHCl3, BF3, CO2, CO (2 marks)
Ans. Polar Compounds: NH3, CHCl3, CO
Non-Polar Compounds: CO2, BF3
Ques. a) Define dipole moment. Mention the SI units of the dipole moment?
(b) Explain how Dipole moment values help in predicting the shapes of the covalent molecules. (5 Marks)
Ans. (a) In a polar molecule, one of the atoms is positively charged and the other has a negative charge. Thus, the molecules have two poles with equal magnitude of the charges. These types of molecules are known as dipolar molecules and possess the dipole moments.
Dipole moment is defined as the product of the magnitude of the positive or negative charge and the distance between the charges.
The SI unit of the dipole moment is Coulomb meter (m) or Debye.
(b) The dipole moment values are quite helpful in determining the general shapes of covalent molecules. Like, for molecules with zero dipole moment will be either linear or symmetrical in shape.
For example: BeF2, CO2, etc. These molecules will possess the dipole moments therefore their shape will not be symmetrical in nature.
Ques. Among this which molecule is more polar NH3 or NF3 Give reason? (2 marks)
Ans. NH3 is more polar than the NF3. Even though the N-F bond is more polar than the N-H bond, but from the net dipole moment we can justify that NH3 is more polar than NF3.
Read Also:
Comments