Patterns and Properties of Metals

Patterns and Properties of Metals

29 November 2021

Watch the reactions of alkali metals with air and water.

• Watch the reactions of alkali metals with air and water.

Reactions of alkali metals

Reactivity of Metals

• As you go down the group in the periodic table, reactivity increases
• As you go across the period, reactivity decreases
• The pattern for non-metals is the opposite

Aluminium

• It is strong and light (not dense), with good electrical conductivity.
• It is reactive, but when it reacts with air, it forms a protective layer of aluminium oxide on its surface, then stops reacting.
• It is used for airplane bodies, power lines, and window frames.

Watch a video of the thermit reaction

Thermit Reaction

• 2 Al(s) + Fe2O3 (s)  2Fe(s) + Al2O3 (s)
• This is an oxidation-reduction (a Redox) reaction.
• Oxidation is the addition of oxygen to a substance.
• Reduction is the removal of oxygen from a substance.
• Which substance is oxidised and which is reduced?

Redox Reactions

• Another way of defining oxidation and reduction:
• Oxidation is the loss of electrons
• Reduction is the gain of electrons

Watch the cation test for aluminium ions.

Watch the cation test for aluminium ions.

Test for aluminium ions

• AlCl3 (aq) + 3 NaOH (aq) → Al(OH)3 (s) + 3 NaCl (aq)
• Al(OH)3 (s) + NaOH (aq) → NaAlO2 (aq) + 2H2O (l)
• Aluminium forms an amphoteric hydroxide – it can act as both an acid and a base.

Transition metals

Properties

• Often make coloured compounds
• Often show more than one valency (form ions with different charges)
• Transition metals and their compounds are often catalysts
• Some are magnetic (iron, cobalt, nickel)

Coloured Compounds

Questions

• P. 212
• Q. 8.8 Give two characteristics of aluminium that make it very useful for construction.
• Q. 8.10 Why does aluminium not corrode like iron?
• P.215
• Q. 8.11 Give three distinctive properties of transition metals
• Q. 8.12 What are two oxidation states of iron in its compounds?
• Q. 8.13 What colour do you associate with copper compounds?
• Q. 8.15 Iron corrodes to form rust. What is the chemical name and formula for rust?
• Q. 8.16 Name an important industrial process for which iron is the catalyst.