Valence shell atomic orbitals nitrogen

Figure 1.16 Reorganization of the valence shell atomic orbitals of nitrogen into four sp hybrid orbitals.

The Lewis symbol for nitrogen, for example, represents the valence electron configuration 2s22pA.12p>112p 1 (see 1), with two electrons paired in a 2s-orbital and three unpaired electrons in different 2p-orbitals. The Lewis symbol is a visual summary of the valence-shell electron configuration of an atom and allows us to see what happens to the electrons when an ion forms. 

Phosphorus is directly below nitrogen in the periodic table. (The relationship of the chemistry of phosphorus to that of nitrogen is somewhat like the sulfur-oxygen relationship discussed in the introduction to Chapter 17.) The phosphorus atom electron configuration is Ne 3.s,23/J3, and it has five outer-shell electrons, as shown by its Lewis symbol in Figure 18.1. Because of the availability of underlying 3d orbitals, the valence shell of phosphorus can be expanded to more than eight electrons. 

Octet Rule Atoms of various elements undergo rearrangements in order to have 8 electrons in their outermost orbit. It is generally referred to as octet rule, e.g. an atom of nitrogen has 5 electrons its valence shell and so must share three more to achieve an octet, thus forming three bonds. Hydrogen is limited to two electrons in its valence shell. 

From the foregoing discussion it appears that as a good approximation the valence shell of Ng consists of 12 molecular orbitals that can be constructed from three 2s and nine 2p orbitals of the nitrogen atoms it accommodates 16 valence electrons. 

We see that sp d hybridization uses an available d orbital in the outermost occupied shell of the central atom. The heavier Group VA elements—P, As, and Sb—can form five covalent bonds using this hybridization. But nitrogen, also in Group VA, cannot form five covalent bonds, because the valence shell of N has only one t and three orbitals (and no d orbitals). The set of t and orbitals in a given energy level (and therefore any set of hybrids composed only of t and p orbitals) can accommodate a maximum of eight electrons and participate in a maximum of four covalent bonds. The same is true of all elements of the second period, because they have only t and p orbitals in their valence shells. No atoms in the first and second periods can exhibit expanded valence. 

Antimony [7440-36-0] is the fourth member of the nitrogen family and has a valence shell configuration of Ss 5p[ The utilization of these orbitals and, in some cases, of one or two 5 6 orbitals permits the existence of compounds in which the antimony atom forms three, four, five, or six covalent bonds. 

The orbitals used are hybridized, sp d hybrids, and are directed to the apices of a trigonal bipyramid (Fig. 23.18). The phosphorus and three of the fluorine atoms lie in a plane the remaining two fluorine atoms are placed symmetrically above and below this plane. To promote an electron in nitrogen, the electron would have to be moved out of the valence shell to a shell of higher principal quantum number. The energy required would be too large to be compensated by the formation of two additional bonds. 

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