Chemical Bonding – Definition, Rules, Types

Chemical bonding is the formation of a chemical bond between two or more atoms, molecules, or ions that results in the formation of a chemical compound. These chemical bonds are what hold the atoms in the resulting compound together.

Chemical bonding is the attractive force that holds various constituents (atoms, ions, etc.) together and stabilizes them through the overall loss of energy. As a result, chemical compounds are dependent on the strength of the chemical bonds between their constituents; the stronger the bonding between the constituents, the more stable the resulting compound.

The inverse is also true: if the chemical bonding between the constituents is weak, the resulting compound will be unstable and will easily undergo another reaction to produce a more stable chemical compound (containing stronger bonds). Atoms try to lose energy in order to find stability. When one form of matter interacts with another, a force is exerted on the first. When the forces of nature are attractive, the energy decreases. When the forces of nature are repulsive, the energy increases. The chemical bond is the attractive force that holds two atoms together.

Theories on Chemical Bonding

Lewis Theory of Chemical Bonding

1. An atom is made up of two parts: a positively charged Kernel (the nucleus plus the inner electrons) and an outer shell.
2. The outer shell can only hold a maximum of eight electrons.
3. The outer shell’s eight electrons occupy the four corners of a cube that surrounds the ‘Kernel.’
4. Atoms with an octet configuration, i.e. 8 electrons in the outermost shell, represent a stable configuration.
5. By forming chemical bonds with other atoms, atoms can achieve this stable configuration. This chemical bond can be formed by gaining or losing an electron(s) (NaCl, MgCl₂), or in some cases by sharing an electron (F₂).
6. In general, an element’s valency is equal to the number of dots in the corresponding Lewis symbol or 8 minus the number of dots (or valence electrons).

Kossel’s theory of Chemical Bonding

1. The highly electronegative halogens and the highly electropositive alkali metals are separated by noble gases.
2. By gaining an electron, halogens can form negatively charged ions. Alkali metals, on the other hand, can form positively charged ions by losing an electron.
3. These negatively and positively charged ions have an 8 electron noble gas configuration in the outermost shell. ns2np6 represents the general electronic configuration of noble gases (except helium).
4. Because unlike charges attract each other, these, unlike charged particles, are held together by a strong electrostatic attraction. MgCl₂, the magnesium ion, and chloride ions, for example, are held together by electrostatic attraction. An electrovalent bond is a type of chemical bond that exists between two oppositely charged particles.

Fajan’s Rule

Fajans’ rule determines whether a chemical bond is covalent or ionic. Kazimierz Fajans first discussed partial covalent characteristics of ionic bonds in 1923. He was able to predict ionic or covalent bonding at the time using X-ray crystallography and attributes such as ionic and atomic radius.

Types of Chemical Bonds

The strength and properties of the chemical bonds formed vary. There are four primary types of chemical bonds that atoms or molecules form to form compounds. Chemical bonds of this type are-

1. Ionic Bonds
2. Covalent Bonds
3. Hydrogen Bonds
4. Polar Bonds

Ionic Bonding

Ionic bonding is a type of chemical bonding in which electrons are transferred from one atom or molecule to another. In this case, an atom loses an electron, which is then gained by another atom. When such an electron transfer occurs, one of the atoms acquires a negative charge and is dubbed the anion. The other atom acquires a positive charge and is referred to as the cation. The strength of the ionic bond is determined by the charge disparity between the two atoms, i.e., the greater the charge disparity between the cation and the anion, the stronger the ionic bond. 

Covalent Bonding

A covalent bond denotes the exchange of electrons between atoms. This type of chemical bonding is common in carbon compounds (also known as organic compounds). The electrons shared by the two atoms now extend around the nuclei of the atoms, resulting in the formation of a molecule.

Polar Covalent Bonding: In nature, covalent bonds can be either polar or non-polar. Electrons are shared unequally in Polar Covalent chemical bonding because the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom. Water is a good example of a polar molecule. Because of the uneven spacing of the electrons between the atoms, there is a difference in charge in different areas of the atom. One end of the molecule is partially positively charged, while the other is partially negatively charged.

Hydrogen Bonding

Hydrogen bonding is a weaker form of chemical bonding than ionic and covalent bonding. It’s a type of polar covalent bonding between oxygen and hydrogen in which the hydrogen acquires a partial positive charge. This means that the electrons are being drawn closer to the more electronegative oxygen atom. This causes the hydrogen to be attracted to the negative charges of any neighbouring atom. This type of chemical bonding is known as a hydrogen bond, and it is responsible for many of water’s properties.

Sample Problems

Question 1: Why do atoms react?

Answer:

Atoms with eight electrons in their final orbit are stable and do not react. Atoms with fewer than eight electrons react with other atoms to gain eight electrons in their outermost orbit and thus become stable.

Question 2: How do atoms react?

Answer:

Atoms in their final orbit with eight electrons are stable and do not react. Atoms with fewer than eight electrons react with other atoms, gaining eight electrons in their outermost orbit and becoming stable.

Question 3: What are the forces that keep reacting atoms together.

Answer:

Because the outer orbitals of atoms overlap in metals, the electrons present in them do not belong to any specific atom, but rather flow over to all atoms and bind them all together (metallic bonding). Atoms that lose and gain electrons combine to form ions, which are held together by electrostatic forces of attraction (Ionic Bond). When atoms give and share electrons equally, the shared electrons serve as a unifying force between them (covalent bond).

Question 4: What are hybridized orbitals?

Answer:

Relatively similar energy sub-orbitals can combine to generate a new set of the same number of orbitals, with all contributing orbitals having the feature of proportionality. They are called hybridized orbitals.

Question 5: Why is oxygen molecule paramagnetic?

Answer:

The oxygen molecule is formed when an oxygen atom shares two electrons with another oxygen atom. The oxygen molecule is paramagnetic, indicating that it contains unpaired electrons. To explain this, a molecular orbital theory has been proposed. According to this theory, atoms lose their orbitals and instead form an equal number of orbitals that cover the entire molecule, giving rise to the term molecular orbital. The filling of these orbitals in increasing energy order results in unpaired electrons, which explains the paramagnetic behaviour of the oxygen molecule.

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