Ions
Chlorine atom, Sodium atom
Chlorine ion, Sodium ion
Sodium and Chlorine atoms.
At the top of the figure above you see a representation
of the atomic structure of the Na and Cl atoms.
The Chlorine atom.
- The Chlorine atom has an equal number of electrons and protons (17e-
and 17p+).
- However this atom is unstable (will react) because the outer shell
of electrons has only seven electrons instead of eight (count them). To
be stable the outer valance shell of electrons should have eight electrons
in it.
The Sodium atom.
- The Na atom has an equal number of electrons and protons (11 e- and
11 p+).
- This atom too is unstable because the outer valance shell of electrons
has only one electron in it. To be stable the outer shell of electrons
should have eight electrons.
When the Na and Cl atoms come into physical contact.
- When the Na and Cl atoms come into physical contact a tremendous reaction
takes place, releasing a great deal of energy.
The Cl ion
- because it has a greater affinity for electrons than the Na atom, the
Cl atom takes an electron from the Na atom.
- When it does so, the outer valence shell of the Chlorine will be filled
with eight electrons and so it will be stable. However, now it has one
more electron than it has protons so it has a net charge of -1. It is now
called the Chloride ion.
- Thus Chloride ions are stable and have a net charge of -1.
The Sodium ion.
- In the reaction the Sodium atom loses an electron to the Chlorine atom.
- Thus it has one more proton than it has electron and has a net positive
charge of +1 and it is now called the Sodium ion.
- In addition, the outer shell now has a full complement of eight electrons
so that the Sodium ion is now stable.
- Thus the Sodium ion has a net charge of +1 and is stable.
When ions of opposite charge meet they are attracted and
form an ionic bond