Chapter 1:
Structure Determines Properties |

Electrons and Orbtials

The electron is the subatomic particle that is fundamental to
chemical
bonding.

Simply put, chemical reactions are about reorganising
bonds And bonds are due electrons So that means chemistry is all about electrons. |

Study Tip: Learn to keep track of electrons ! Pay attention
to
charges. You will find that if you know where the electrons are and what they are doing, then it is much easier to master organic chemistry. |

Electrons have always been thought of as **particles**
since their
discovery in 1897.

But in 1924 it was also suggested that electrons also have **wave**
like properties.

This is the concept of "wave-particle duality" due to De Broglie.

**QUESTION : **Can you think
of an example of particle type and wave type properties ? **ANSWER**

In 1926 Schrodinger was able to show that electrons in a
hydrogen atom could be described by a **wave function, Y**.

Electrons are often described as being in **orbitals **around an atom that
are mathematical "constructs" based on the wave function, **Y**,
that describes the motion of an electron.

An orbital is, more correctly, a mathematical function, **
4pr ^{2}Y^{2}**,
that describes the region of high probability in 3D space, around a nucleus,
where an electron may be found. Orbitals are commonly represented by the boundary
surfaces that encloses the region where there is a 90-95 % probability of finding
the electron.

In organic chemistry one needs to be most
familiar with the **s- **and**
p-type** orbitals. These orbitals can be described by
using
**quantum
numbers**. Quantum numbers arise from the wave functions and
quantum
mechanics.

The orbitals for the electrons in **carbon**, and the necessary
quantum numbers are given below. The nucleus of the carbon atom
would
reside
at the centre of the x,y,z coordinate.

*You should be familiar with the
meaning of quantum numbers, and
how to describe an orbital using its quantum numbers or what orbital a
set of quantum numbers defines.*

Try some questions. If
you are struggling you'll need to review the
meaning of quantum numbers.

The **electron configuration** of an
atom describes how the electrons
of an atom are arranged.

e.g.electron configuration of carbon

simple 1s ^{2}2s^{2}2p^{2}short form [He]2s ^{2}2p^{2}orbital energy diagram

*You should be familiar with how to determine an electron
configuration for an atom and identify the valence electrons. You should
be able to identify both ground and excited state electron configurations.*

You should now try some questions. If you are still having trouble, you should review how to determine electron configurations.

© Dr. Ian Hunt, Department of Chemistry |