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Elements and compounds

Elements and compounds. Grade 9. Definition of an element. An element is a substance that cannot be made into anything simpler by means of a chemical reaction.

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Elements and compounds

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  1. Elements and compounds Grade 9

  2. Definition of an element • An element is a substance that cannot be made into anything simpler by means of a chemical reaction. • The atoms of an element all have the same numbers of protons. There are over a hundred different elements and they are arranged in the periodic table.  

  3. Definition of a compound • Compounds contain more than one element. • The elements in a compound are not just mixed together: they are joined by strong forces called chemical bonds. • You will not find any compounds in the periodic table. • Compounds do not have the same properties as the elements they contain. • A compound is a substance that can be made into something simpler by means of a chemical reaction.  

  4. Sodium metal is very reactive • Chlorine is a poisonous gas. • They combine to form sodium chloride which has different properties. • It is non poisonous and non reactive.

  5. Why do elements form compounds • Atoms tend to have the maximum number of electrons in their outer levels. • They achieve this by bonding with other atoms. Electron will move from Na to Cl

  6. Ionic Compound • An ionic compound is made up from metals and non metals. • The metal will be written before the non metal. • CaF2 MgO NaCl K2S

  7. Naming Ionic compounds • The name of the metal will not change • The name of the non metal will change into the “root of the word + ide” • Oxygen will change into oxide • Sulphur will change into sulphide • Chlorine will change into chloride

  8. Naming Ionic compounds • CaO • calcium oxide • KCl • Potassium chloride • FeS • Iron sulphide • MgS • Magnesium sulphide • Al2O3 • Aluminium oxide

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