Chapter 1: Where are the Electrons ?

Learning Objectives:

• Terminology of chemical structure
• Understanding atomic structure
• Properties of atomic orbitals

Summary

Chemistry is often traditionally divided into organic, inorganic and physical areas. These areas could certainly be further subdivided and there is also lots of overlap between each of them too. However, in general terms, organic chemistry is the study of compounds containing carbon.

Why the focus on a specific element from the periodic table?

• Historically, it was believed that compounds from living organisms posessed a unique "vital force" that humans could not create in a laboratory (disproved in 1828 when Friedrich Wohler accidently made urea in the laboratory from ammonium cyanate).
• Carbon is unlike most elements in the periodic table because it can form stable molecules containing different types of bonds:
  • bonds to several other carbon atoms (this allows chains to form),
  • single, double or triple bonds,
  • bonds to many other elements,
• As a result, many different bonding patterns can occur and hence there are millions of organic compunds known.

The aim of studying organic chemistry is to understand the properties and reactions of organic compounds. These properties (physical, chemical and biological) are controlled by the interactions between these molecules and these properties are dictated by the types of bonds within those molecules. As you will see later, understanding the location of electrons is especially important as it is the arrangement and the rearrangement of the electrons that creates the bonds between the atoms and their reactions. Hence, organic chemistry is really about understanding what the electrons are doing and the first step in that process is knowing where they are.

Although you may feel that most of this chapter is review from your previous Chemistry course(s), many students are not as strong as they need to be to survive the adventure that lies ahead, so make sure you start your organic course in good shape.

Here is a short list of topics that cause many students problems that relate to fundamental material.

Structure

• Molecules : what are they made of ?
• Atoms : what are they made of ?
• Atomic Orbitals
• Some important properties of atoms (e.g. size, electronegativity, ionisation)

• Formal Charge
• Bonding
• Bond types: Ionic, Covalent, Polar Covalent
• Lewis Structures
• The Shapes of Molecules and Molecular dipoles
• Constitutional Isomers
• Drawing curly arrows
• Resonance
• Acids and Bases

• More practice problems ?

© Dr. Ian Hunt, Department of Chemistry