Nitrogen atom, electronic configuration

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. 

D Hund s rule states that the electrons fill orbitals so that there is the maximum number of parallel spins. For example, this is why the valence electrons for a nitrogen atom are configured... 

The two electrons in the ls-orbital may, of course, be regarded as being in an inner-shell and are, as such, outside our present considerations). Here (as in 1.2), 2pa denotes a p-orbital which is symmetrical with respect to reflection in the plane of the molecule. In the isolated nitrogen atom, the configuration is... 

The nitrogen atom in ammonia (NH3) forms three covalent bonds. Nitrogen s electronic configuration shows that it has three unpaired valence electrons (Table 1.2), so it does not need to promote an electron to form the three covalent bonds required to achieve an outer shell of eight electrons—that is, to complete its octet. 

At this point it is useful to introduce the concept of valence electrons—that is, the electrons in the outermost (highest) principal energy level of an atom. For example, nitrogen, which has the electron configuration ls 2s 2p, has electrons in principal levels 1 and 2. Therefore, level 2 (which has 2s and 2p sublevels) is the valence level of nitrogen, and the 2s and 2p electrons are the valence electrons. For the sodium atom (electron configuration ls 2s 2p 3s or [Ne]3s ) the valence electron is the electron in the... 

Figure 5. Niels Bohr came up with the idea that the energy of orbiting electrons would be in discrete amounts, or quanta. This enabled him to successfully describe the hydrogen atom, with its single electron, In developing the remainder of his first table of electron configurations, however, Bohr clearly relied on chemical properties, rather than quantum theory, to assign electrons to shells. In this segment of his configuration table, one can see that Bohr adjusted the number of electrons in nitrogen s inner shell in order to make the outer shell, or the reactive shell, reflect the element s known trivalency.

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. 

The AG values for the rotation around the C3-N bond were obtained by the coalescence method and kinetic measurements of the equilibration of isolated and configurationally established cis-trans isomers of type 232. The barrier of rotation is considerably lower than in ordinary immonium cations, e.g. 233 AG is decreased by electron-withdrawing substituents at the nitrogen atom, whilst at the three-ring the opposite effect is observed. 

Although the explanation will be provided later, the configuration on the right is lower in energy than the one on the left. As we have already stated, electrons remain unpaired as long as possible. Therefore, the carbon atom that has the electron configuration Is2 2s2 2p2 has two impaired electrons. In a similar way, the nitrogen atom has three electrons in the 2p orbitals,... 

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