Homework. Period Three Trends

Period Three Trends

Don’t panic we will do bonding next and the trends can be simplified:

Sodium, magnesium and Aluminium are metals. Therefore, they have typical metallic properties i.e. shiny, malleable, and conduct electricity. The delocalized electrons can move and therefore, maintain the metallic bond even if the shape is changed, in addition they can move and so an electric current can flow. Si, P S Cl and Ar are non- metals. Ar is a noble gas and so exits as atoms but the others have covalent bonds, either as a giant covalent structure i.e. Si or as simple covalent molecules. The melting point will depend very much on the type of covalent bonding. Giant covalent substances will have very high melting points, as the strong covalent bonds need to be broken. However, simple molecular substances will have relatively low melting points due to the weak forces of attraction between the molecules (Van der Waal’s). 

The metallic oxides are ionic. These are basic and produce hydroxide solutions. Al₂O₃ is an exception as it has both kinds of bonding, ionic and covalent and so can react with acids and bases. It is said to be amphoteric. However, in water in does not dissolve and so won't affect the pH.

The covalent oxides are acidic; they react with water to form an acid. 

The ionic oxides are neutral or slightly acidic. Any slight acidity is just due to protons being pulled off water molecules, releasing H⁺ ions. The smaller and more highly charged the ion, the more this happens.

The covalent chlorides react with water to form two acids (usually), one of them being HCl.  ACl₃ is strange in that it is actually a covalent compound and is made up of a metal and a non-metal. It produces HCl when it reacts with water. 

Your homework is to: 

• Produce a neat table of results from your experimental observations
• Write an equation for all of the reactions that occurred. (include the oxides and chlorides that we didn’t have)
• Make conclusions from your results about the trends of the elements, oxides and chlorides of period three that you saw
• Explain the conclusions that you made and relate them to the type of bonding

Use your notes form the lesson, the notes / links on the blog and your text book