ELECTRONS IN ATOMS - Chemical Fundamentals of Geology and Environmental Geoscience - page 98

Review

As the following chapters will show, these princi-
ples, together with the energy level scheme shown in
Figure 5.7, form the foundation upon which modern
inorganic chemistry is built.

The important conclusions of this chapter may be
summarized in the following terms:

(a) The behaviour of an electron, when trapped in an
atom, is dominated by its wave-like nature. The
electron distributes itself in space about the nucleus
in a manner analogous to a stationary wave on a
fixed string.
(b) Each electron in an atom can adopt one of a variety of
'waveforms' having different spatial configurations
of electron density. These are called orbitals. Each
corresponds to a solution of the Schrödinger wave
equation. An orbital's size and shape are defined by
the values of various quantum numbers, in a manner
reminiscent of the harmonics of a vibrating string.
(c) Electron energy in the atom is quantized, like the
frequency of a guitar string (and for the same rea-
son). Each orbital has its own discrete energy level
and collectively they give rise to an electron energy
structure resembling an irregular set of pigeon-
holes (Figure 5.7), which in qualitative terms is
common to all types of atom.
(d) Two electrons can share the same orbital provided
that they have opposed 'spins'. Each electron nor-
mally occupies the lowest-energy orbital in which
space is available. Energy considerations thus dic-
tate the geometric distribution of electron density
about the nucleus.

Further reading

Atkins, P., Overton, T., Rourke, J., et al . (2010) Inorganic
Chemistry , 5th edn. Oxford: Oxford University Press.
Barrett, J. (2002) Atomic Structure and Periodicity . Cambridge:
Royal Society of Chemistry.
Fyfe, W.S. (1964) Geochemistry of Solids. An Introduction.
Chapter 2. New York: McGraw Hill.

Exercises

5.1 Work out which electron orbitals have the follow-
ing quantum numbers:

n l

2 1

3 0

4 3

5 2

5.2 Determine the electron configurations of the
chemical elements having the atomic numbers 6,
11, 13, 17, 18, 26.