Chemical Bonding and Molecular Structure

In Chemistry, chemical bonding is an attractive force that binds various constituents such as atoms and ions together and stabilises them by losing overall energy. Thus, it’s quite evident that the strength of the compound depends on the bond formed. Also, the chemical bonding is proportional to the stability which means, the stronger the bond between the compounds more will be the stability of that molecule. On the other hand, the molecular structure is a vast discussion, hence, this article will cover the types of structures along with their basic description.

Theories associated with bonding

1. Lewis Theory

In 1916, Gilbert Lewis successfully explained the formation of chemical bonding on the basis of the inertness of noble gases. According to this theory, an atom consists of a kennel (positively charged) and an outer shell. The electrons occupy the outer shell and surround this kennel. Thus, the atoms having 8 electrons attain a stable configuration. This means atoms form a stable bond when their outermost shell is completely occupied. Also, only valence electrons (electrons present in the outermost shell) take part in the chemical bond formation.

1. Kossel’s theory

Noble gases have the tendency to separate highly electropositive alkali metals and highly negative alkali earth metals. These halogens have the tendency to form negatively charged ions and noble metals form positively charged alkali metals. These negatively and positively charged ions have a stable configuration with 8 electrons and are given by ns2np6. These oppositely charged particles undergo bond formation due to the electrostatic force of attraction and the bond is called an electrovalent bond.

Types of bonds

Depending on the reaction, we can predict the type of bond formed during the reaction

1. Ionic bond

The bond formed due to the transfer of electrons is called an ionic bond. Here, one atom loses an electron and becomes a positively charged atom also called a cation, whereas the other atom which has gained an electron, now becomes negative and is called an anion. The bonds are stronger when the charge disparity between cations and anions is more.

1. Covalent bond

The bond formed due to sharing of electrons between two atoms is called a covalent bond. Compounds containing Carbon mostly form a covalent bond.

1. Polar bond

When the electron distribution between the two atoms forming a bond is uneven then the polar bond is formed. The dividing line between the covalent bond and an ionic bond is the Polar bond. Usually, any atoms with a difference in electronegativities less than 0.4 are considered to be a nonpolar covalent bond.

1. Metallic bonds

When an electron cloud is formed around the ion centre then the bond formed is called a metallic bond. Compared to covalent bonds and ionic bonds, metallic bonds have high electrical conductivity and thermal conductivity.

While the molecular structure is a vast discussion, the current article will cover the types of structures along with their basic description. 

Molecular structure

Depending on the ideal molecular structures which were predicted by combining lone pair and bonding pair, a few structures are illustrated below. The most common factor that distinguishes the mentioned structure is the bond angle, which is nothing but the angle between two adjacent bonds in a molecule.

1. Linear geometry- In linear molecules, the bond angle is 1800 and the structures are set in a linear fashion.
2. Trigonal planar- In trigonal planar molecules the bond angle is 1200 and the structures are triangular in one plane.
3. Angular – Angular molecules have a V-shaped or a bent shape with a bond angle of 1050.
4. Tetrahedral- Molecules with tetrahedral structures have four faces sharing bonds with the central metal atoms and having no lone pair of electrons. The bond angle in the case of tetrahedral structure is 109.470
5. Octahedral- Molecules with octahedral structures have eight faces with a bond angle of 900.
6. Trigonal pyramidal- structures having triangular bases with pyramidal structures come under Trigonal pyramidal structures. In the case of trigonal pyramidal structures, there are 3 pairs of bonded electrons with one unshared electron which distorts the structure. Due to the presence of lone pair, the structure inhibits lone pair-lone pair repulsion thereby lowering the bond angle compared to tetrahedral structures. 

Conclusion: 

To know more about structures and geometry one can read and understand the Valence-shell electron pair repulsion theory. As the no. of electrons in the molecule changes its overall structure is transformed, this proves that chemical structure can be modified due to electron transformation and lead to different geometries, some of them mentioned above. On the other hand, different chemical bonding is associated with 2 different theories namely Lewis’s theory and kernel theory. Once we understand these theories it’s easier to predict whether the chemical bond present in the molecule is polar, ionic, covalent, or metallic. These bonds have different characteristics which can easily be differentiated by the chemist. The present article discussed chemical bonding and bond structures of different atoms, basic differences between them, bond angles, and how structures are formed.