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Ions.
An atom has the same
number of protons and electrons.
An atom has no overall electric
charge.
If an atom loses or
gains electrons it is no longer called an atom.
It is called an ion. An ion has a full outer shell
of electrons.
An ion has an electric charge.
All chemical reactions involve
atoms trying
to get
a full outer shell of
electrons.
The total number
of atoms is the same before and
after the reaction.
When an atom reacts with
another atom, it will either
1. Lose electrons to form a stable positive
ion.
2. Gain electrons to form a stable negative ion.
or 3. Share
electrons to form a stable
molecule.
Sodium has 1 electron
in its outer shell. It is in group 1 of the
periodic table.
When sodium reacts with non-metals
(for example chlorine) it will lose
its outer
electron. Its outer shell will
then have no electrons.
It is as though the outer shell has
vanished. The next shell in is full.
This full inner
shell becomes the new outer
shell. Sodium is now stable.
The unstable sodium atom
loses its outer
electron
to become a stable sodium
ion.
The sodium ion still has 11 protons (11 positive charges)
but now only 10 electrons
(10 negative charges).
The sodium ion has an extra positive charge, shown by the + sign.
All group 1
metals will form a 1+ ion when they react with non-metals.
The charge on the ion can also be shown as
and the electron
structure written as [2,
8]+
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Copyright © 2008 Dr. Colin France. All Rights Reserved.
