Giant ionic structures
The Electrically charged particle, formed when an atom or molecule gains or loses an electron/electrons. in a A substance formed by the chemical union of two or more elements., such as sodium chloride, are arranged in a giant ionic structure (also known as a giant ionic lattice). This regular arrangement results in the formation of a A solid containing particles (atoms, molecules or ions) joined together to form a regular arrangement or repeating pattern..
The diagram shows part of the crystal lattice of sodium chloride:
This pattern is repeated in all directions, giving a giant three-dimensional lattice structure in sodium chloride crystals.
Because of the strong A force of attraction between particles with opposite charges. between them, it takes a great deal of energy to separate the positive and negative ions in a crystal lattice. This means that ionic compounds have high melting points and boiling points.
Solid ionic compounds do not conduct electricity because the ions are held firmly in place. The ions cannot move to To allow electricity, heat or other energy forms to pass through. the The movement of electrically charged particles, for example, electrons moving through a wire or ions moving through a solution.. But when an ionic compound melts, the charged ions are free to move. Therefore, molten ionic compounds do conduct electricity.
When a crystal of an ionic compound dissolves in water, the ions separate. Again, the ions are free to move 鈥 so a solution of an ionic compound in water also conducts electricity.
Ionic lattices
The oppositely charged ions in a giant ionic lattice are held together by strong ionic bonds (electrostatic forces of attraction) in a huge three-dimensional structure.
Take a look at this example 鈥 it鈥檚 a crystal lattice of sodium chloride.
Diagrams like this are best drawn by starting with one type of ion (eg Na+) and then following each line from this ion to all neighbouring ions and making them the other type of ion (eg Cl鈥). No line should join identical ions.
Explaining melting points [Higher tier only]
It takes a lot of energy to overcome the strong electrostatic forces of attraction between oppositely charged ions, so ionic compounds have high melting and boiling points. However, some have higher melting points than others.
The greater the Property of matter that causes a force when near another charge. Charge comes in two forms, positive and negative. For example, a negative charge causes a repulsive force on a neighbouring negative charge. on the ions, the stronger the forces holding them together. Sodium chloride is made from Na+ ions and Cl鈥 ions and has a melting point of 801掳C. Magnesium oxide is made from ions with two charges (Mg2+ and O2鈥) and so has a much higher melting point of 2,852掳C.