# Chemical Structure and Bonding

## Objectives

At the end of this curricular unit, students should have aquired knowledge and skills which will allow them to:

Apply general concepts of quantum mechanics

Predict atomic and mlecular properties

Predic Lewis Strucutures.

Predict electronic structure and molecular geometry through Valence Bond Theory and Molecular Orbital Theory

Predict molecular properties (bond order and distance, paramagnetism, acid/base behaviour, nucleofilicity and electrofilicity, ioniztion energy, electron afinity, conductor, semi-conductor or insulating properties, etc.)

Use Molecular Orbital Theory to predict and rationalize chemical reactivity in simple molecules.

## General characterization

##### Code

3683

##### Credits

6.0

##### Responsible teacher

António Gil de Oliveira Santos

##### Hours

Weekly - 4

Total - 57

##### Teaching language

Português

### Prerequisites

No minimum requirements.

### Bibliography

R. L. Deckock, H. B. Gray, *Chemical Structure and Bonding*, University Science Books, Sausalito, California,1989

### Teaching method

The program of Chemical Structure and Bonding is transmitted in Portuguese during 39 hours of theoretic-practical classes (3 hours per week), followed by 18 hour of pratical classes (1.5 hours per week) dedicated to the resolution of typical exercises and discussion with the students.

### Evaluation method

**Overall assessment of the course:**

Throughout the semester, students complete two (2) **mandatory** partial tests with the same weigh for the final score (50% each). The grade (**final score**) will be the weighted average of the partial test scores summed with the grade correction obtained through class attendance (see bellow, Frequency). Only students who obtain at least 9.50 in the final score will be approved.

**Frequency** (Exclusion from final examination):

Student attendance to the classes will be accounted to the** final score** in accordance with the document "**Faltas.pdf**", available in "**Documentação de Apoio/Outros**". This system is applicable to all students, independent of the number of inscriptions in the UC. If the penalty due to the student attendance is higher than 10.50 valores (penalty due to absence to theoretical and pratical classe, see document "**Faltas.pdf**"), the student will be excluded from the final examination (Recurso).

Absence justifications must be submitted within one week of the date of absence.

**"RECURSO" Examination:**

Students with a **final score** below 9.50 will have access to the exam - **Recurso**. This examination will consider all the course syllabus. For these students, the **final score** will be the sum of the examination grade and the grade of the attendance (see Frequency above). Only students with a **final score** equal or higher than 9.50 values will be approved.

## Subject matter

Historical review of the atomic models of Thompson''''s (plum pudding) and Rutherford (planetary).

Experimental evidence: atomic spectra and photoelectric effect. Planck/Einstein energy-frequency relation.

Introduction to Bohr''''s model. Postulates.

De Broglie''''s relation. Heisenberg''''s Uncertainty Principle. Phenomenon of electron interference as experimental evidence of a dual character, wave/particle, of the electron.

Classical general equation of waves. Deduction of the Schrodinger equation in one dimension. Model of a particle in a unidimensional box. Bidimensional and tridimensional boxes. Quantum numbers and dimensionality of the box.

Schrodinger equation in two and three dimensions.

Quantum numbers and electronic configuration. Energy hierarchy of atomic orbitals in the hydrogen atom and in polyelectronic atoms. Penetrating effect of atomic orbitals. Effective nuclear charge.

Periodic properties of the elements: Atomic radius, ionic radius, ionization energy, electronic affinity and electronegativity. Pauling’s electronegativity scale.

Lewis structures. Resonance hybrids. Molecular geometry according to the valence-shell electron-pair repulsion method. Concept of dipolar moment.

Valence bond theory (VBT). Notion of hybrid atomic orbital. Examples of molecules with non-bonding pairs and of molecules with multiple bonds.

Molecular orbital theory (MOT). Evaluation of the expansion coefficients of atomic orbitals in the molecular orbitals of the hydrogen molecule. Concept of integral overlap (S), exchange (beta) and Coulomb (alpha) integrals. Normalization condition of molecular orbitals. Huckel appriximation. Construction of molecular orbital diagrams. Molecular orbital theory applied to heteroatomic and polyatomic molecules. Walsh diagrams. Aromaticity as described by molecular orbital theory.

Chemical reactivity as described by VBT and by MOT. Frontier orbital theory. Lewis acids and bases. Lewis adducts (e.g. NH3.BF3). Symmetry rules. Concerted reactions.