Fluorine atomic orbitals

MO Coefficients for Fluorine Atomic Orbitals Computed from F19 Hyperfine Interactions"... 

We calculated the overlap populations for each SF molecule as well. Table II shows the overlap populations between the sulfur and fluorine atomic orbitals. The values are per bond averages. For all the molecules the overlap populations of the S3p- 2p and S3d- 2p pairs are larger than the others. The... 

In this simple treatment it has been assumed that the fluorine atomic orbitals do not mix, which is not strictly true. More detailed calculations show that the F 2s orbital makes a significant contribution to the bonding orbital. 

In xenon difluoride, the electronic structure shows three lone pairs around the xenon, and two covalent bonds to the two fluorine atoms hence it is believed that here xenon is using one p (doublepear) orbital to form two bonds ... 

This simple model is readily extended to other atoms. The fluorine atom (electron configuration lsz2s22p5) has a half-filled p orbital ... 

The formation of the BeF2 molecule can be explained by assuming that, as two fluorine atoms approach Be, the atomic orbitals of the beryllium atom undergo a significant change. Specifically, the 2s orbital is mixed or hybridized with a 2p orbital to form two new sp hybrid orbitals. (Figure 7.12). 

In the BeF2 molecule, there are two electron-pair bonds. These electron pairs are located in the two sp hybrid orbitals. In each orbital, one electron is a valence electron contributed by beryllium the other electron comes from the fluorine atom. 

A fluorine atom has the orbital occupancy shown below ... 

We see that the neutral fluorine atom has seven valence electrons that is, seven electrons occupy the outermost partially filled cluster of energy levels. This cluster of energy levels, the valence orbitals, contains one electron less than its capacity permits. Fluorine, then, has the capacity for sharing one electron with some other atom which has similar capacity. If, for example, another fluorine atom approaches, they might share... 

Now consider the possibility of the bonding that might occur if a fluorine atom encounters a hydrogen atom. Again fluorine has an opportunity to share electrons with a second atom having a partially filled valence orbital ... 

We see that the bonding of a fluorine atom to another fluorine atom or to a hydrogen atom can be explained in terms of sharing electrons so as to fill the partially filled valence orbitals. This... 

The experimental quantities shown in (14) and (15) indicate that the F ion is more stable than a fluorine atom and an electron. Energetically, a fluorine atom wants" another electron. It is profitable to express reaction (12) in terms of orbital occupancy ... 

There is another possible consequence of a collision between two fluorine atoms. The two atoms can remain together to form a molecule. Each atom has a valence electron in a half-filled orbital. We can imagine these two atoms orienting so that these half-filled" orbitals overlap in space. Then the half-filled" valence orbital of... 

It is a simple matter to predict that oxygen will form a stable compound with two fluorine atoms, F20. The orbital representation is ... 

We see that each oxygen atom has residual bonding capacity. Each atom could, for example, react with a hydrogen atom to form hydrogen peroxide, as shown in electron dot representation (26). Each oxygen atom could react with a fluorine atom to form F2O2. In short, each oxygen atom is in need of another atom with mi electron in a half-filled valence orbital so that it can act as a divalent atom. 

The diatomic molecule of fluorine does not form higher compounds (such as F3, F4, - ) because each fluorine atom has only one partially filled valence orbital. Each nucleus in Fs is close to a number of electrons sufficient to fill the valence orbitals. Under these circumstances, the diatomic molecule behaves like an inert gas atom toward other such molecules. The forces that cause molecular fluorine to condense at 85°K are, then, the same as those that cause the inert gases to condense. These forces are named van der Waals forces, after the Dutch scientist who studied them. 

In NF3, with each atom having four orbitals in its outer shell, there is no way for one fluorine atom to be attached to the nitrogen atom by a double bond and the other two by single bonds and to provide orbitals for the... 

The three structures of type 4 are unstable for two reasons the presence of electric charges of the same sign on adjacent atoms, and the use by the nitrogen atom of only three orbitals. The contribution of these structures to the normal state of the molecule is accordingly small, and we may take it to be zero. Also, structures of type 3, with a double bond and the transfer of the positive charge to a fluorine atom, are stabilized by the formation of an additional covalent bond with use of the fourth orbital and may accordingly make a greater contribution to the normal state moreover, there is an extra factor 2 for the six structures of type 3 over the three of type 1. 

Consider the orbital interactions of a hydrogen atom and a fluorine atom as they combine to form a molecule of hydrogen fluoride. The electron in the hydrogen atom occupies the 1 S orbital. According to the orbital overlap... 

The Lewis structure of hydrogen fluoride shows three lone pairs on the fluorine atom. These nonbonding electrons are localized in atomic orbitals that belong solely to fluorine. Remembering that one of the fluorine 2 p orbitals is used to form the H—F bond, we conclude that the three lone pairs must occupy the remaining pair 2 p orbitals and the 2 s orbital of the fluorine atom. 

A similar situation arises when two fluorine atoms approach each other. The first valence orbitals to overlap are the 2 p orbitals pointing along the axis that joins the atoms. Figure 10-5 shows that bond formation in molecular fluorine results from the strong directional overlap of these two atomic 2 p orbitals. 

To visualize bond formation by an outer atom other than hydrogen, recall the bond formation in HF. One valence p orbital from the fluorine atom overlaps strongly with the hydrogen 1 S orbital to form the bond. We can describe bond formation for any outer atom except H through overlap of one of its valence p orbitals with the appropriate hybrid orbital of the inner atom. An example is dichloromethane, CH2 CI2, which appears in Figure 10-11. We describe the C—H bonds by 5 -I S overlap, and we describe the C—Cl bonds by 5 - 3 p... 

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