Diatomic molecule of elements

Fig. 5.12 Simplified molecular orbital energy levels for diatomic molecules of elements in the second period, assuming no mixing of s and p orbitals. The three 2p orbitals are degenerate, that is, they all have the same energy and might also be...

Figure 9-5 shows molecular orbital energy level diagrams for homonuclear diatomic molecules of elements in the first and second periods. Each diagram is an extension of the... 

The validity of molecular orbital theory is supported by its ability, unlike valence bond theory, to correctly predict certain properties of homonuclear diatomic molecules of elements in the first and second periods. What prediction would valence bond theory make about the paramagnetism of these molecules For which molecules does molecular orbital theory make a different prediction ... 

To illustrate molecular orbital theory, we apply it to the diatomic molecules of the elements in the first two periods of the periodic table. 

Among the diatomic molecules of the second period elements are three familiar ones, N2,02, and F2. The molecules Li2, B2, and C2 are less common but have been observed and studied in the gas phase. In contrast, the molecules Be2 and Ne2 are either highly unstable or nonexistent. Let us see what molecular orbital theory predicts about the structure and stability of these molecules. We start by considering how the atomic orbitals containing the valence electrons (2s and 2p) are used to form molecular orbitals. 

Predicted and Observed Properties of Diatomic Molecules of Second Period Elements... 

C09-0047. Hydrogen forms diatomic molecules with elements from Group 1 of the periodic table. Describe the bonding in LiH and include a picture of the overlapping orbitals. 

Note that a pair of hydrogen atoms bonded together is a hydrogen molecule. Seven elements, when uncombined with other elements, form diatomic molecules. These elements are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. They are easy to remember because the last six form a large 7 in the periodic table ... 

FIGURE 3.7 Energy level diagrams for diatomic molecules of second-row elements. Early members of the series follow the diagram shown in (b), whereas later members follow (a). 

In writing these configurations for diatomic molecules of second-row elements, we have omitted the electrons from the Is orbitals because they are not part of the valence shells of the atoms. When considering the oxygen molecule, for which the a orbital arising from the combinations of the 2pz orbitals lies lower in energy than the 7r orbitals, we find that the electron configuration is... 

Homonuclear diatomic molecules of second-period elements B2, C2, and N2 ... 

The oxidation numbers of Cl and Br in (a) have changed. Cl has changed from 0 to -1, while Br has changed from -1 to 0. (In diatomic molecules, the elements are considered to be in the uncombined state thus rule 1 applies.) There is no change in any oxidation number of any element in (b). Thus, (a)... 

Compound A molecular substance composed of atoms and formed by a chemical reaction of two or more elements. The molecules of the new compound have properties very different from the properties of the elements that formed the compound. An example is when two diatomic molecules of hydrogen gas (2Hj) combine with one diatomic molecule of oxygen gas (Oj) to form two water molecules (2HjO), which have none of the properties of the original two substances. 

Homonuclear Diatomic Molecules of the Second Short Period Elements, E ... 

The electronic configurations of the homonuclear diatomic molecules of the elements of the second period, and some of their ions, are given in Table 4.1. 

Oxygen, fluorine, and man. These three molecules can be treated with the same energy diagram that we have been using for other diatomic molecules of the second-row elements. As we shall see shortly, the intervening molecules, B, C-. and N2. require additional considerations, which lead to an alteration in (he relative energies of the molecular orbitals. 

The situation close to that described above for sulfur is characteristic for the chal-cogenide elements. Atomic selenium [1,26,82-86] and tellurium [86] are part of di-, tri-, and polynuclear clusters, while diatomic molecules of these elements, when acting as ligands, have mostly a bridge function 52. Examples of di- and trinuclear monochalcogenide compounds are the complexes 53 and 54 [82-85] ... 

Most substances consist of two or more elements joined by chemical bonds. For example, consider the chemical combination of the elements hydrogen and oxygen shown in Figure 1.6. Oxygen, chemical symbol O, has an atomic number of 8 and an atomic mass of 16, and it exists in the elemental form as diatomic molecules of 02. Hydrogen atoms combine with oxygen atoms to form molecules in which two H atoms are bonded to one O atom in a substance with a chemical formula of H20 (water). A substance such as H20 that consists of a chemically bonded combination of two or more elements is called a chemical compound. In the chemical formula for water the letters H and O are the chemical symbols of the two elements in the compound and the subscript 2 indicates that there are two H atoms per one O atom. (The absence of a subscript after the O denotes the presence of just one O atom in the molecule.)... 

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