Fluorine orbital diagram

If we now consider a planar molecule like BF3 (D3f, symmetry), the z-axis is defined as the C3 axis. One of the B-F bonds lies along the x-axis as shown in Figure 5.9. The symmetry elements present for this molecule include the C3 axis, three C2 axes (coincident with the B-F bonds and perpendicular to the C3 axis), three mirror planes each containing a C2 axis and the C3 axis, and the identity. Thus, there are 12 symmetry operations that can be performed with this molecule. It can be shown that the px and py orbitals both transform as E and the pz orbital transforms as A, ". The s orbital is A/ (the prime indicating symmetry with respect to ah). Similarly, we could find that the fluorine pz orbitals are Av Ev and E1. The qualitative molecular orbital diagram can then be constructed as shown in Figure 5.10. 

It is readily apparent that the three a bonds are capable of holding the six bonding electrons in the a t and e molecular orbitals. The possibility of some 7r-bonding is seen in the molecular orbital diagram as a result of the availability of the a2" orbital, and in fact there is some experimental evidence for this type of interaction. The sum of the covalent radii of boron and fluorine atoms is about 152 pm (1.52 A), but the experimental B-F bond distance in BF3 is about 129.5 pm (1.295 A). Part of this "bond shortening" may be due to partial double bonds resulting from the 7r-bonding. A way to show this is by means of the three resonance structures of the valence bond type that can be shown as... 

The VSEPR model makes some assumptions. Primarily, it assumes that orbitals from neighboring atoms overlap and electrons are shared within the common region of space. Another assumption is that only unpaired electrons are involved in bonding. This latter assumption is where things get a bit sticky, so an alternative approach is needed. Take the fluorine atom, for instance, whose orbital diagram is shown in Figure 7.11 ... 

Fluorine has one unpaired electron and, as you know, forms one bond. Similarly oxygen, whose orbital diagram is... 

Figure 10.89. Qualitative molecular orbital diagram for FeF, involving the fluorine 2p and iron 4.v. 3 d atomic orbitals [244], The energies of the iron non-bonding orbitals (15, 9 a, 4 it) are very close to that of the 10cr antibonding orbital.

We have used 12 electrons to form the S—F bonds, which leaves 36 electrons. Since fluorine always follows the octet rule, we complete the six fluorine octets to give the structure on the right above. This structure uses all 48 valence electrons for SF6, but sulfur has 12 electrons around it that is, sulfur exceeds the octet rule. How can this happen There are several ways to approach this situation. The classical explanation for molecules like SFg involves using the empty 3d orbitals on the third-period elements. Recall that the second-row elements have only 2s and 2p valence orbitals, whereas the third-row elements have 3s, 3p, and 3d orbitals. The 3s and 3p orbitals fill with electrons in going from sodium to argon, but the 3d orbitals remain empty. For example, the valence-orbital diagram for a sulfur atom is... 

Fluorine is our first example. Take a look at its electron configuration and orbital diagram. 

Fluorine is in group 7A, so it has seven valence electrons. The orbital diagram for the valence electrons of fluorine is... 

Using boxes for the orbitals, write out the orbital diagrams for (a) nitrogen, (b) fluorine, and (c) vanadium. 

The S—F (T-bonds involve the radial 2p orbitals, and therefore the partial MO diagram that we construct for SFg focuses only on these fluorine orbitals. The wavefunctions that describe the LGOs for the Fg fragment in SFg are derived as follows. We first work out how many of the six radial 2p orbitals are unchanged under each Ojj S5Tnmetry operation. The following row of characters gives the result ... 

The electron configurations and orbital diagrams for fluorine (nine electrons) and neon (ten electrons) are... 

Boron, atomic number 5, occurs naturally as two isotopes, and B, with natural abundances of 19.9% and 80.1%, respectively, (a) In what ways do the two isotopes differ from each other Does the electronic configuration of differ from that of B (b) Draw the orbital diagram for an atom of B. Which electrons are the valence electrons (c) Indicate three major ways in which the Is electrons in boron differ from its 2s electrons, (d) Elemental boron reacts with fluorine to form BF3, a gas. Write a balanced chemical equation for the reaction of solid boron with fluorine gas. (e) AHf for Bp3(g) is —1135.6 kl/mol Calculate the standard enthalpy change in the reaction of boron with fluorine, (f) When BCI3, also a gas at room temperature, comes into contact with water, the two react to form hydrochloric acid and boric add, H3BO3, a very weak acid in water. Write a balanced net ionic equation for this reaction. 

The S—F (T-bonds involve the radial 2p orbitals, and therefore the partial MO diagram that we constmct for SFg focuses only on these fluorine orbitals. The wavefunctions... 

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