S orbital overlap

Covalent bonds are formed when atomic orbitals overlap. The overlap of atomic orbitals is called hybridization, and the resulting atomic orbitals are called hybrid orbitals. There are two types of orbital overlap, which form sigma (cr) and pi (tt) bonds. Pi bonds never occur alone without the bonded atoms also being joined by a ct bond. Therefore, a double bond consists of a O bond and a tt bond, whereas a triple bond consists of a ct bond and two tt bonds. A sigma overlap occurs when there is one bonding interaction that results from the overlap of two s orbitals or an s orbital overlaps a p orbital or two p orbitals overlap head to head. A tt overlap occurs only when two bonding interactions result from the sideways overlap of two parallel p... 

FIGURE 3.11 When electrons (depicted as t and 1) in two hydrogen ls-orbitals pair and the s-orbitals overlap, they form a cr-bond, which is depicted here by the boundary surface of the electron cloud. The cloud has cylindrical symmetry around the internuclear axis and spreads over both nuclei. 

Figure 56. Change in d -S orbital overlap resulting from twisting of the dithiolene ligand (trigonal twist) and folding of the MS2C2 chelate (sulfur-fold).

In this molecule the carbon atoms are sp2 hybridized. This means that there is sp2 bonding between the two carbon atoms. The s orbital from the hydrogen atoms will bond with the p orbitals from the carbon atoms as well. There will be no s to s orbital overlap in this case. 

For example, if two S orbitals overlap, they form two molecular orbitals one is a bonding orbital, a, and the other is an antibonding orbital, a. Electronic excitation of a molecule occurs when an electron from one molecular orbital is promoted to another of higher energy. Such transitions are written as ... 

Formation of a o antibonding MO. When two I s orbitals overlap out of phase, they interact destructively to form an antibonding MO. The positive and negative values of the wave functions tend to cancel out in the region between the nuclei, and a node separates the nuclei. 

For example, VB theory proposes that the central B atom in the BF3 molecule is SI hybridized. Figure 11.3 shows the three si orbitals i n the trigonal plane, with the third 2p orbital unhybridized and perpendicular to this plane. Each s[ orbital overlaps the 2p orbital of an F atom, and the six valence electrons— three from B and one from each of the three F atoms—form three bonding pairs. 

In the formation of a molecule, the valence electrons (electrons that make the bond between the atoms) are affected by both nuclei, and they move in molecular orbitals whose shape is governed by the shape of the individual atomic orbitals. For example, in a bond between two hydrogen atoms, each of the electrons that is to form the bond between the atoms is in an s orbital these s orbitals overlap to form a molecular orbital between the two nuclei. This orbital is known as a sigma orbital. If bonding takes place between p orbitals, the bond is in two parts (at the end of each lobe of the p orbital) and is known as a pi orbital. 

To describe the multiple bonding in ethylene, we must distinguish between two kinds of bonds. A cylindrical shape about the bond axis. It is formed either when two s orbitals overlap, as in H2 (Figure 10.25A), or when an orbital with directional character, such as a p orbital or a hybrid orbital, overlaps another orbital along their axis (Figure 10.25B). The bonds we discussed in the previous section are a bonds. 

The alkali metal diatomics [1-3] have been studied in the gas phase and/or at very low temperatures in the condensed phase, often supported by theoretical investigations. To date, all combinations of homo- and heterodiatomic, M-M or M-M, molecules (M, M = group 1 metal) from Li to Cs have been experimentally observed (see Table 2.1) [4-26]. Data from Table 2.1 includes theoretical investigations into diatomics containing Fr and the not-yet-discovered element 119 (eka-francium), denoted as 119. In all of these molecules, the two metal atoms Interact via single bonds, derived from s-orbital overlap, to yield molecules with an ground state. The metal-metal bond lengths in... 

The first atom has an s orbital with a certain level of energy. When a second atom is added, its s orbital overlaps with that of the previous atom, and forms two molecular orbitals - one bonding and the other antibonding. If we add a third atom, its s orbital overlaps with the previous two molecular orbitals to form three new molecular orbitals, and so on. Hence, by adding n atoms, we form s molecular orbitals, which, as new atoms are added, extends the available energy domain covered by molecular orbitals. 

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