Electronic structures and processes discusses the arrangement of electrons in atomic orbitals and molecules. It covers the filling of electron shells in the first four periods of the periodic table. The document also discusses applications of electronic structures in organic chemistry, physical chemistry, analytical chemistry, and spectroscopy. It describes how computational methods can be used to model structures, reaction mechanisms, transition states, and spectroscopic properties.

1. ELECTRONIC STRUCTURES
AND PROCESSES

2. INTRODUCTION
• In atomic physics and quantum
chemistry, electron configuration is the
arrangement of electrons of an atom, a
molecule, or other physical structure. It
concerns the way electrons can be distributed
in the orbital of the given system
(atomic or molecular for instance).

4. The first period
• Hydrogen has its only electron in the 1s orbital
- 1s1, and at helium the first level is completely
full - 1s2.

5. The second period
• These levels all have the same energy, and so
the electrons go in singly at first.

6. • B 1s22s22px1
• C 1s22s22px12py1
• N 1s22s22px12py12pz1
The next electrons to go in will have to pair up
with those already there.
• O 1s22s22px22py12pz1
• F 1s22s22px22py22pz1
• Ne 1s22s22px22py22pz2

7. The third period
• all the second level orbitals are full, and so
after this we have to start the third period
• The pattern of filling is now exactly the same
as in the previous period, except that
everything is now happening at the 3-level.

8. short version
Mg 1s22s22p63s2 [Ne]3s2
1s22s22p63s23px23py13
S [Ne]3s23px23py13pz1
pz1
1s22s22p63s23px23py23
Ar [Ne]3s23px23py23pz2
pz2

9. The beginning of the fourth period
• At this point the 3-level orbitals aren't all full -
the 3d levels haven't been used yet. But if you
refer back to the energies of the orbitals, you
will see that the next lowest energy orbital is
the 4s - so that fills next.

10. • K 1s22s22p63s23p64s1
• Ca 1s22s22p63s23p64s2

11. APPLICATIONS OF ELECTRONIC
STRUCTURES

12. Organic Chemistry
• organic chemistry is generally the second
course sequence for students majoring in
chemistry or chemical engineering

13. Fundamentals of Structure-Reactivity
Relationships
• From their first courses in chemistry, all
students have at least a rudimentary
knowledge of acids as proton donors. Thus, a
simple computational exercise they can carry
out the first time they use modeling software
is one in which they construct a set of related
organic protic acids and model electronic
charge density associated with the acid
proton.

14. Experimental Design and Formulation
of Testable Hypotheses
• We have used two other somewhat less usual
pedagogical applications of the computational
features of modeling software to support the
laboratory portion of the organic chemistry
course.

15. Transition States and Reaction
Mechanisms
• From about mid-way through a first course in
organic chemistry references to reaction
mechanism, transition state structures, and
the interplay of thermodynamic control and
kinetic control are frequent.

16. Physical Chemistry
• The physical chemistry curriculum can be
divided into the following major segments:
thermodynamics and thermochemistry,
chemical kinetics, and quantum chemistry.

17. Quantum Chemistry
• When using most electronic structure
computational packages, the user is faced
with a number of different computational
approaches: molecular mechanics, ab-initio,
semi-empirical, and density functional.

18. Thermo chemistry
• An important topic in physical chemistry is the
ability to obtain thermo chemical information
on unstable species or reaction intermediates
and transition state structures.

19. Chemical Kinetics
• An excellent example of using electronic
structure computations is to have students
construct a potential energy diagram along a
reaction pathway.

20. Chromatography
• As our first example, we describe how
electronic structure computations can be used
effectively in developing a student's
understanding of chromatographic
separations.

21. Spectroscopy
• Another important topic in analytical
chemistry is spectroscopy, the study of the
interaction of light with matter.

22. Predicting Trends
• In advanced analytical chemistry courses it is
possible to enhance understanding of
spectroscopic trends by performing
calculations for a particular family of
molecules.

23. Vibrational Spectroscopy
• At this point we wish to address briefly the
applications of electronic structure
computations in advanced analytical
spectroscopy courses and their potential
overlap with advanced inorganic courses.