The valence bond VB model applied to F2, O2 and

Consider the formation of F2. The ground state electronic configuration of F is fie]2s 2p, and the presence of the single unpaired electron indicates the formation of an F—F 

Consider the formation of F2. The ground state electronic configuration of F is [He]2y 2p, and the presence of the single unpaired electron indicates the formation of an F—F single bond. We can write down resonance structures 2.12 to describe the bonding in F2, with the expectation that the covalent contribution will predominate. 

In a diamagnetic species, all electrons are spin-paired a diamagnetic substance is repelled by a magnetic field. A paramagnetic species contains one or more unpaired electrons a paramagnetic substance is attracted by a magnetic field. 

Within VB theory, the wavefunction that describes the bonding region between two H atoms in H2 can be written in the form  

Explain the meaning of this equation, including the reason why the factor N is included. 

It is incorrect to draw an equilibrium symbol between two resonance structures. The correct notation is a double-headed arrow. Explain why the distinction between these notations is so important. 

The formation of O2 involves the combination of two O atoms with ground state electronic configurations of ls 2 2p. Each O atom has two unpaired electrons and so VB theory predicts the formation of an 0=0 double bond. Since VB theory works on the premise that electrons are paired wherever possible, the model predicts that O2 is diamagnetic. One of the notable failures of VB theory is its inabihty to predict the observed paramagnetism of O2. As we shall see. 

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