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Ionic compounds are formed between metals and non-metals. They are usually hard crystalline solids with high melting points, e.g. the melting point of Sodium fluoride is 1265K. Their crystalline shapes reflect the internal symmetry in which millions of tiny ions are arranged in perfect lattice structures. 30/11/2018 nrt

The ions are formed when the elements react with one another. The evidence for crystal structures comes from X-ray diffraction studies. The lattice is held together by electrostatic attractions, called IONIC BONDS. The ions are formed when the elements react with one another. The elements react in an attempt to become more stable. 30/11/2018 nrt

The Formation of Sodium Chloride The Sodium and Chlorine atoms need full outer shells of electrons to achieve stability. The Sodium atom has one electron in its outer shell. The Chlorine atom has one space in it’s outer shell. 30/11/2018 nrt

Stability is achieved by the donation of an electron from the Sodium atom to the Chlorine atom. 30/11/2018 nrt

- + The Sodium atom takes on an electronic configuration of 2,8 and becomes a positively charged sodium ion. The Chlorine atom takes on an electronic configuration of 2,8,8 and becomes a negatively charged chloride ion. 30/11/2018 nrt

An ionic compound, Sodium chloride (NaCl) is the product. The two ions attract one another as a result of their opposite electrostatic charges. 30/11/2018 An ionic compound, Sodium chloride (NaCl) is the product. nrt

When hydrogen and chlorine gas react together a very stable ionic compound, Hydrogen chloride (HCl) is the product. H2 + Cl2  2HCl 30/11/2018 nrt

The diagram shows how Sodium ions and chloride ions pack together in a single plane of a Sodium chloride crystal. 30/11/2018 nrt

This is a 3-d view of a ball and stick model of a Sodium chloride lattice (face centred cube)... Key Sodium ion Chloride ion 30/11/2018 nrt

Magnesium and Chlorine also form an ionic compound called Magnesium chloride (MgCl2). The diagram shows that the Magnesium atom has two spare electrons in its outer shell. 30/11/2018 nrt

Stability is achieved by the donation of an electron from the Magnesium atom to each of the two Chlorine atoms. 30/11/2018 nrt

- 2+ Both Chlorine atoms take up an electronic configuration of 2,8,8 and become negatively charged chloride ions. The Magnesium atom now has an electronic configuration of 2,8 and becomes a dipositively charged magnesium ion. 30/11/2018 nrt

- 2+ The ions attract one another as a result of their opposite electrostatic charges. An ionic compound, Magnesium chloride, Mg2+(Cl-)2 is the product. Therefore the formula of Magnesium chloride is MgCl2. 30/11/2018 nrt

The Crystal Lattice of Sodium chloride 30/11/2018 nrt

The form of the crystal lattice is determined by the size of the ions. The relative sizes of the Sodium and chloride ions mean that they pack together as shown in the diagram. The bonds are represented by cylinders. The ions are held together by electrostatic attraction. 30/11/2018 nrt

As more ions are added to the structure, the lattice takes shape. Each ion has six nearest neighbour ions of opposite charge. 30/11/2018 nrt

This image shows a corner of a large cubic crystal model of Sodium chloride. 30/11/2018 nrt

Gypsum Crystals Gypsum is a variety of Calcium sulphate (CaSO4). This is an ionic compound, but it’s internal symmetry is different to that of Sodium chloride. Why...? 30/11/2018 nrt

Caesium and Chlorine also react to form an ionic compound with the formula CsCl. Caesium atoms have an outer shell with one electron. The ions are formed similarly to those in Sodium chloride. 2Cs + Cl2  2CsCl Caesium chloride has the following lattice structure... 30/11/2018 nrt

In the Caesium chloride lattice, each ion has eight nearest neighbour ions of opposite charge. 30/11/2018 nrt

The lattice formed by Caesium and chloride ions is called a body centred cubic lattice. 30/11/2018 nrt

Ionic substances usually have the following properties... 1. They are hard, glassy solids. Amethyst 2. They have a regular crystalline shape. 3. They are usually soluble in aqueous solvents. 4. They have high melting points. 5. In the solid state, they are non-conductors of electricity but when molten or in aqueous solution, they conduct electricity freely and are decomposed by the current. This process is known as electrolysis. 30/11/2018 nrt

Ruby is Al2O3 plus traces of Cr2O3 Stibnite is Sb2S3 Ionic Crystals Wulfenite is PbMoO4 Smokey Quartz is SiO2 30/11/2018 nrt