Chemical Bonding and Molecular Structure - Notes, Topics, Books, FAQs

Chemical bonding is the study of bonds that exist between the atoms or molecules. This chapter explains why only certain atoms combine with each other and make a new product and their arrangement in a definite shape. There are various theories such as VSEPR, valence bond theory, and the molecular orbital theory that will explain all the phenomena in detail. Bonding is not just an instance but it is nature's way to take every atom or molecule to its most stable state.

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This Story also Contains

1. Notes For Chemical Bonding And Molecular Structure
2. Important Topics:
3. How to Prepare for Chemical bonding?
4. Prescribed Books

In our body itself, all the macromolecules like DNA, RNA, Proteins, etc are held together with the help of this chemical bonding. All the structures are held together with the help of this chemical bond, either the bond is stronger or weaker. Based on the strength of the bonds, the stability of the structure is determined. The melting and boiling point, etc are the important properties that are determined by the strength of the chemical bond. This chapter is usually liked by every student as it is very easy and it holds enough distribution of marks in Board exams and other competitive exams like JEE and NEET.

Notes For Chemical Bonding And Molecular Structure

In this section, you will study the important topics of the chapter, overview, formulae, and some important tips and guidelines for the preparation of the chapter at the best.

Important Topics:

There are the following important topics that are covered in this chapter:

Ionic bonding:

Ionic bonds or Electrovalent bonds are formed from the electrostatic attraction between oppositely charged ions in a chemical compound.

Fazan’s rule:

Fajan’s Rule helps to predict whether a chemical bond is ionic or covalent. It states that the size and charge of cations and anions determine the type of bond forms.

Lewis Electron Dot Structures:

Lewis Electron Dot Structures is the important topic of this chapter in this we study how the electrons are arranged in the elements to bond with another element.

Limitations Of The Octet Rule:

Limitations Of The Octet Rule is also an important topic. The octet rule has various limitations it does not apply to all states, it does not count the number of electrons, and it does not apply to elements with fewer than eight electrons.

Formal charge and Lewis dot structures:

A hypothetical charge assumed to be an atom in a molecule is called a formal charge, assuming that electrons are shared equally between atoms. It is very helpful in predicting a molecule's reactivity and structure.

Bond Parameters - Bond Order, Angle, Length, And Energy:

Bond Parameters - Bond Order, Angle, Length, And Energy is the most important topic for knowing the stability of the bond or the compounds form after bonding.

Valence Shell Electron Pair Repulsion (VSEPR) theory:

Vsepr Theory is based on the repulsion between the pairs of valence electrons. The electrons repel each other in order to minimize the repulsion.

Valence Bond Theory (VBT):

The overlapping between two incompletely filled atomic orbitals leads to the formation of a bond between two atoms is called Valence Bond Theory.

Hybridization and its types:

The process of combining two atomic orbitals to create a new type of hybridized orbitals is called Hybridisation is also an important topic.

Molecular Orbital Theory (MOT):

Molecular Orbital Theory explains how molecules form and behave by describing the distribution of electrons in a molecule. It has a different principle which tells molecular orbitals are equal to the atomic orbitals.

Also read,

• Formation of Ionic Compounds
• Pcl5 Hybridization
• Lattice Energy
• Drago's Rule
• Pi Bonds
• Molecular Geometry
• Dipole Moment
• Van Der Waals Forces
• Hydrogen Bonding

Overview of Chemical Bonding:

All atoms in this universe seek to achieve their stable electronic configuration in the “Noble gas” configuration. Atoms except Hydrogen achieve this stable noble gas configuration by following the octet rule in the following ways:

(i) Ionic bond: In this type of bond, metals, and non-metals take part in the bond formation by the complete exchange of electrons as depicted in the picture below:

(ii) Fazan's Rule: This rule states that in every ionic bond, there is always some percentage of covalent character. This covalent character depends upon the size of the anion and cation, a charge of the anion and cation. As the charge on the cation is larger and its size is smaller its polarising power increases and thus the covalent character increases. Similarly for an anion, if its charge is higher and its size is also larger then its polarisability increases and thus the covalent character increases.

(iii) Covalent bond: This type of bond formation takes place by the sharing of electrons between the non-metals. The picture given below shows its representation.

In this chapter, you will learn about the Lewis dot structures. Lewis dot structure is the simple representation of the molecules formed by the covalent bonds. However, in this concept, the geometry of the molecules needs to be determined, which is one of the major drawbacks of this concept. So to overcome these drawbacks, several advanced theories have been given by scientists and they are VSEPR, VBT, and MOT.

(iv) Kossel Lewis Approach: This is the simplest model for explaining the structures of the chemical bond. This approach considers the central atom as a sphere and electrons as point charges around it. Now, these point charges electrons are shared between atoms or completely exchanged between atoms and form the covalent and ionic bond respectively. After the formation of these bonds, all the atoms engaged in bonding achieve the stable noble gas configuration.

(v) VSEPR Theory:

• In VSEPR theory, it was said that the shapes of the molecules are determined by the combination of a lone pair of electrons and bond pair electrons.

• These electrons repel each other. In order to minimize the repulsion, these electrons arrange themselves at the maximum distance and hence form the geometry.

• Some common geometries of the molecules are tetrahedral, square planar, octahedral, etc.

(vi) Valence Bond Theory:

• The bond formation takes place only by the valence orbitals containing unpaired electrons and spinning in opposite directions.

• Bond formation takes place by partial overlapping of orbitals. So, according to this theory, various kinds of overlapping occurs during bond formation like s-s overlapping, s-p overlapping, p-p overlapping, and pi bond (lateral overlapping of p orbital).

(vii) Hybridization:

• This concept says that during the time of bond formation, the first intermixing of orbitals of comparable energies occurs to produce the new orbitals, also known as hybrid orbitals, and then bond formation occurs. The hybridization concept eliminates all the drawbacks that were not solved by the earlier theories.
• The number of hybrid orbitals produced is equal to the number of atomic orbitals.
• The hybrid orbitals are identical in shape, size, energy, etc.
• The hybrid orbitals always form a sigma bond.

For example, BeF₂ This bond is not explained by VSEPR and VBT, thus hybridization explains its bond formation and structure. This is explained below:

Finally, at the end of this chapter, you will learn about a new theory i.e. “Molecular Orbital Theory”. This theory is applicable to only diatomic molecules like O₂, N₂, F₂, etc. This theory explains several things like electron distribution in bonding and antibonding molecular orbitals, bond order, and paramagnetic or diamagnetic nature of molecules.

How to Prepare for Chemical bonding?

Although this chapter is a part of physical chemistry it is a completely theory-based chapter. For preparing this chapter, a formula or numerical practice is not required. To solve the questions of this chapter, first, you must have a complete understanding of Atomic structure and classification of elements and periodicity in properties chapters. For a good hold in this chapter, you must give a mock test after completing the theory and you need to go through class 11th NCERT book thoroughly.

Prescribed Books

For chemical bonding and molecular structure, first, you need to finish the theory thoroughly from the NCERT book and then solve the examples and questions given in the book. Apart from this, if you want to prepare for the advanced level of competitive exams like JEE and NEET, you must read the book - O.P Tandon or P. Bahadur. Meanwhile, in the preparation, you must continuously take the mock tests for internal assessment.