Lewis Theory of Chemical Bonding
The Lewis theory of chemical bonding, also known as the Lewis electron dot theory, was proposed by the American chemist Gilbert N. Lewis in 1916. It provides a simple model to understand how atoms bond together to form molecules by focusing on the arrangement of valence electrons.
According to the Lewis theory, atoms gain, lose, or share electrons in order to achieve a stable electron configuration similar to that of noble gases. Noble gases have complete outer electron shells, making them highly stable and unreactive. Lewis recognized that other atoms tend to react in ways that allow them to acquire a similar electron configuration.
Key points of Lewis’s Theory of Chemical Bonding are as follows:
- An atom is made up of two parts: a positively charged Kernel (the nucleus plus the inner electrons) and an outer shell that contains electrons.
- The outmost shell can only hold a maximum of eight electrons.
- The outer shell’s eight electrons occupy the four corners of a cube that surrounds the ‘Kernel.’
- Atoms with an octet configuration, i.e., 8 electrons in the outermost shell, represent a stable configuration.
- 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).
- Atoms with eight electrons in their outer shell are said to have a stable configuration. Atoms with fewer than eight electrons in their outer shell will try to gain electrons to achieve a stable configuration. Atoms with more than eight electrons in their outer shell will try to lose electrons to achieve a stable configuration.
- Chemical bonds are formed when atoms share, gain, or lose electrons to achieve a stable configuration.
- The number of dots in a Lewis symbol represents the number of valence electrons in an atom.
- The valency of an atom is the number of valence electrons that an atom can share, gain, or lose to achieve a stable configuration.
The key concept in the Lewis theory is the valence shell, which consists of the outermost energy level of an atom. Lewis represented valence electrons as dots around the atomic symbol. For example, the element oxygen (O) has six valence electrons, so it is represented as O with six dots around it.
Explanation of Bonds using Lewis Theory
The Lewis theory uses electron-dot symbols to depict the valence electrons of atoms and then suggests that atoms form bonds by sharing or transferring these electrons. The two main types of chemical bonds described by the Lewis theory are:
- Ionic Bonds: In ionic bonding, atoms transfer electrons to form ions with opposite charges. The transfer occurs from an atom with low ionization energy (tends to lose electrons) to an atom with high electron affinity (tends to gain electrons). The resulting oppositely charged ions are held together by electrostatic forces, creating an ionic compound. For example, sodium (Na) donates an electron to chlorine (Cl) to form sodium chloride (NaCl).
- Covalent Bonds: In covalent bonding, atoms share electrons to achieve a stable electron configuration. This type of bonding typically occurs between nonmetals. The shared electrons are represented by pairs of dots or lines between the atoms. For example, in a molecule of water (H2O), oxygen shares electrons with two hydrogen atoms.
Chemical Bonding
Chemical Bonding as the name suggests means the interaction of different elements or compounds which defines the properties of matter. Chemical bonds are formed when either at least one electron is lost to another atom, obtaining at least one electron from a different atom, or transferring one electron to another atom. In this article, we will learn about the theories of chemical bonding such as Lewis’s theory which explains the Lewis structure of any compound, Kossel’s Theory, and Fajan’s rule. So, let’s begin the journey of Chemical Bonding.
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