Chemical Bonding
What makes atoms form different substances that we see all around us. It is how atoms bond with each other which is explained by Chemical bonding.
Chemical bonding is defined as the attractive force that holds atoms or ions together and stabilizes the atoms and ions using the loss of energy. The chemical compounds formed are based on the strength of the chemical bonds between the different elements involved. The strength of the chemical bond determines the properties and stability of the said compound.
Classification of Chemical Bonding
Chemical bonds might be classified into different types based on the nature of bonding, chemical reactions, and the type of elements involved. Also, there are different theories that govern chemical bonding.
Lewis Theory of Chemical Bonding:
Lewis articulates that the atom is a positively charged nucleus with its outer layers (technically called outer shells) filled with electrons.
Any given atom can fit a maximum of 8 electrons in its outermost shell and the electrons present in the outermost shell are known as valence electrons.
According to Lewis’ theory of chemical bonding, the atoms having a full 8 electrons in its outermost shell or ‘valence shell’ is said to have an “Octet Configuration”. And all atoms with an octet configuration are the most stable ones.
In fact, the fundamental principle for atoms to form chemical bonds with other atoms is to attain a stable configuration (Octet Configuration). Depending on the number of valence electrons an atom has, it accordingly forms bonds with other atoms and attains stability.
Lewis had come up with the idea of ‘Lewis Dot Structure’ for demonstrating chemical bonding on paper. According to his theory, on paper, the valence electrons of the atoms are depicted in the form of dots around their chemical symbol.
An example of this is the formation of NaCl. Sodium (Na) has 1 electron in its outermost shell and Chlorine (Cl) has 7 electrons in the outermost shell. So, Na atoms and Cl atoms form NaCl compounds, which have an octet configuration.
Distinguishing Chemical Bonds:
Depending on the gain, loss, or sharing of electrons among atoms, we characterize the chemical bonds formed between 2 given atoms. The number of electrons lost, gained, or shared is directly connected to the strength of the chemical bond, and based on these 2 theories, we might categorize chemical bonds as:
Ionic Bond:
Ionic chemical bonding is one type of chemical bonding, wherein atoms transfer (loss or gain) their electrons as part of the bond. This type of chemical bonding results in the formation of two types of atoms, which are cation and anion. The atom gaining the electron attains a negative charge and it is known as anion the atom losing the electron is called the cation and it attains a positive charge.
Covalent Bond:
Covalent bonding usually involves elements of the 4th group in the periodic table. It is because they have exactly 4 valence electrons, which means they need to gain or lose exactly 4 electrons to attain an octet configuration, which is theoretically impossible. Hence, unlike ionic bonding which involves the total transfer of electrons, these types of electrons share their electrons and form covalent chemical bonding.
Hydrogen bonding:
Among the different types of chemical bonds, hydrogen bonding is the weakest chemical bonding. The perfect example of hydrogen bonding is the bond between hydrogen and oxygen in the water molecule. The nature of bonding in the water molecule is predominantly the reason for most of its properties. A hydrogen bond is sub-classified into intermolecular hydrogen bonding (which means the hydrogen bond formed between two adjacent molecules) and intramolecular hydrogen bonding (this is hydrogen bonds formed in the molecule).
Coordinate Bonding:
In Coordinate chemical bonding, the shared pair of electrons come from the same atom. It is one form of covalent bonding, which is alternatively termed as a dipolar bond or a dative bond. Similar to ionic bonding, this type of binding also involves the formation of acceptors and donors. For an in-depth understanding of organic chemistry and co-ordinate chemistry, it is very essential to understand the features of coordinate bonding.
Features of Chemical Bonds:
Bond Enthalpy: It is defined as the amount of energy required to break one mole of a bond into free gaseous atoms. Bond Enthalpy is denoted in terms of KJ mol-1. It can also be called Bond Dissociation Enthalpy.
Bond Length: The distance between the centers of nuclei between atoms involved in a chemical bond is known as the bond length. The bond length of a chemical bond is directly proportional to its Bond dissociation enthalpy.
Bond Order: The number of bonds formed between 2 atoms or molecules depicts its bond order. A higher bond order provides great stability to the compound. The maximum bond order a compound can possess is 3.
Conclusion
Chemical bonding is defined as the formation of chemical bonds between two or more atoms or molecules by means of loss of energy by the atoms or molecules. Based on the nature of chemical bonds, they are classified in 4 different types, and they possess different characteristics. Understanding chemical bonds between atoms can help us understand the properties of that compound.