![]() Today, the modern versions of these theories are competitive with each other in terms of accurately describing real behavior. In 1931, Pauling published a paper on valence bond theory entitled, "On the Nature of the Chemical Bond." The first computer programs used to describe chemical bonding used molecular orbital theory, but since the 1980s, principles of valence bond theory have become programmable. 1 In general, there are two classifications for bond cleavage: homo lytic and hetero lytic, depending on the nature of the process. ![]() This can be generally referred to as dissociation when a molecule is cleaved into two or more fragments. Valence bond theory was developed to describe resonance and orbital hybridization. In chemistry, bond cleavage, or bond fission, is the splitting of chemical bonds. Note that sigma bond has been referred to as the strongest type of covalent bond because the extent of overlap is maximum in case of orbitals involved in the formation of the sigma bond. The sigma bond in the a hydrogen molecule (shown in red) is formed by overlap of a pair of 1 s orbitals, one from each hydrogen atom. Sigma bonds (\sigma) () are the strongest type of covalent bond, formed by head-on overlapping of atomic orbitals. In 1928, Linus Pauling combined Lewis's pair bonding idea with the Heitler-London theory to propose valence bond theory. Sigma bond ( bond ): A covalent bond formed by overlap of atomic orbitals and/or hybrid orbitals along the bond axis (i.e., along a line connected the two bonded atoms). The atomic orbitals overlap along the inter-nuclear. This theory described chemical bond formation between hydrogen atoms in the H2 molecule using Schrödinger's wave equation to merge the wavefunctions of the two hydrogen atoms. The covalent bond formed by the axial overlap of atomic orbitals is called a sigma bond. Sigma Bond: This type of covalent bond is formed by the axial overlapping of half-filled atomic orbitals. Quantum mechanics was applied to describe bonding properties in the Heitler-London theory of 1927. Lewis proposed these structures in 1916, based on the idea that two shared bonding electrons formed chemical bonds. Valence bond theory draws from Lewis structures. All right, we just said that a sigma bond is a head-on overlap of orbitals. ![]()
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