What are they?
What are Ions?
•
An atom has an overall charge of zero
since it always has the same number of
protons and electrons.
•
An ion is formed when an atom (or group
of atoms) gains or loses at least one
electron
•
Because ions have unequal numbers of
protons and electrons, ions have either a
positive or a negative ionic charge.
Positive Ions
A
cation is a positively charged ion.
The diagram below shows how a cation forms.
The sodium atom loses its
outermost electron to form
an ion. The sodium ion is
stable because its outer
orbit is full, like that of
neon.
 The
name of a cation is the same as the name of
the element.
Example: Na+ is called a sodium ion.
 Positively charged ions are usually formed from
atoms of metal elements.
Negative Ions
 An
anion is a negatively charged ion.
The diagram below shows how an anion forms.
The fluorine atom gains
an electron in its
outermost shell to form
an ion. The fluoride ion is
stable because its outer
orbit is full, like that of
neon.
 To
name an anion, add –ide to the stem of the
element’s name.
Example: F- above is a fluoride ion.
 Negatively charged ions are usually formed
from atoms of non-metal elements.
Why are Ions formed?

Atoms gain or lose enough electrons
to have a full outer orbit of eight
electrons. This arrangement of
electrons is most stable and the ion
is less likely to undergo a chemical
change than the atom from which it
was formed.
Why are Ions important?
•
Many ions are critical for good
health, such as sodium ions,
phosphorous ions, iron ions, and
calcium ions to name a few.
Why are Ions important?
•
It is critical, however, that their
concentrations are regulated. Your
body needs some sodium to operate
properly, but too much sodium can
lead to heart or kidney disease. Too
little iron in your body can lead to a
condition known as anemia.