Electronic structure theory is an area of theoretical chemistry that is focused on calculating the arrangement and energies associated with configurations of electrons in molecules. This can include predicting the structure of a molecule, the most probable arrangement of its electrons, its reactivity, and different excited states of the molecule. For reasons we won’t go into, this is not an easy task, and the electronic structure of molecules cannot be solved exactly, even with very powerful computers. Most theoretical chemists working in this area develop approximations for calculating the true electronic structure of molecules and on testing these approximations against available experimental data to continue to improve existing methods. The electronic properties of molecules play a vital role in determining their stability and reactivity, so despite being challenging, it’s a problem well worth trying to solve.