Molecular interpretation of Gibbs energy

As previously stated, although thermodynamic arguments can be developed without any reference to the existence and behavior of atoms and molecules, it is nevertheless informative to interpret the arguments in terms of molecular structure. 

Consider first the dissociation of hydrogen molecules into hydrogen atoms 

We know that when hydrogen atoms are brought together and combine there is evolution of heat, which means that the enthalpy goes to a lower level that is 

The entropy change is also negative when hydrogen atoms combine, because the atoms have a less ordered arrangement than the molecules  

The Gibbs energy change for the combination process at constant temperature is made up as follows  

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