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2. 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.
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3. 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.
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4. 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.
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5. Stability is achieved by the donation of an electron from the Sodium atom to the Chlorine atom.
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6. - +
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.
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7. 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.
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8. When hydrogen and chlorine gas react together a very stable ionic compound, Hydrogen chloride (HCl) is the product.
H2 + Cl2  2HCl
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9. The diagram shows how Sodium ions and chloride ions pack together in a single plane of a Sodium chloride crystal.
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10. 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
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11. 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.
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12. Stability is achieved by the donation of an electron from the Magnesium atom to each of the two Chlorine atoms.
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13. - 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.
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14. - 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.
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15. The Crystal Lattice of Sodium chloride
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16. 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.
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17. As more ions are added to the structure, the lattice takes shape.
Each ion has six nearest neighbour ions of opposite charge.
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18. This image shows a corner of a large cubic crystal model of Sodium chloride.
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19. 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...?
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20. 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...
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21. In the Caesium chloride lattice, each ion has eight nearest neighbour ions of opposite charge.
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22. The lattice formed by Caesium and chloride ions is called a body centred cubic lattice.
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23. 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.
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24. Ruby is Al2O3 plus traces of Cr2O3
Stibnite is Sb2S3
Ionic Crystals
Wulfenite is PbMoO4
Smokey Quartz is SiO2
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