gcsescience.com 3 gcsescience.com
Electron Shells (energy levels).
Electrons in atoms occur in
shells (shown as circles around the
nucleus).
The shells can also be called
energy levels.
We will use the term shell rather than
energy level but either is acceptable.
The maximum number of
electrons in each shell,
going from the middle to the
outside, is 2, 8, 8, 18.
Below is a picture of a potassium
atom. Its electron structure is
2, 8,
8, 1.
An atom which has the maximum number of
electrons in its outer shell
will be stable. This means that it will not react with
other atoms.
It belongs to a group called the
noble
gases. The electron
shells
are said to be
full. The inner shells of an
atom are always
full.
If the outer
shell of an atom has
less than its maximum number of
electrons
(see potassium above) then it will not be stable.
It will react
with other atoms to get a full
outer shell.
gcsescience.com Contents The Periodic Table Index Quizzes gcsescience.com
Copyright © 2008 Dr. Colin France. All Rights Reserved.
