5.2.1 Ionic bonding
5.2.1.2 Ionic bonding
The non-metal atoms in group 0 are inert (unreactive)
because they have a full outer shell or a stable electron configuration.
Ne has 10 electrons so the electronic configuration 2, 8
Ar has 18 electrons so the electron configuration 2, 8, 8
When a metal atom reacts with a non-metal atom, electrons in the outer shell of the metal atom are transferred.
Metal atoms lose electrons to become positively charged ions.
Non-metal atoms gain electrons to become negatively charged ions.
The charge on metal ions:
a group 1 metal loses 1 electron from its outer shell and forms a 1+ ion
a group 2 metal loses 2 electrons from its outer shell and forms a 2+ ion
a group 3 metal loses 3 electrons from its outer shell and forms a 3+ ion
The charge on non-metal ions:
a group 6 metal loses 1 electron from its outer shell and forms a 1+ ion
a group 7 metal loses 2 electrons from its outer shell and forms a 2+ ion
The ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7
have the stable electronic structure of a noble gas (Group 0).
The electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram
eg for sodium chloride.
5.2.1.3 Ionic compounds
An ionic compound is a giant structure of ions.
Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding.
The structure of sodium chloride can be represented in the following forms:
5.2.2.3 Properties of ionic compounds
Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions.
These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds.
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.