3.2.3

Metallic Behaviour & Oxides

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Metallic and Non-Metallic Behaviour

The vertical and horizontal trends in the periodic table can be used to predict and explain the metallic and non-metallic behaviour of elements.

Metals

Metals

  • Typically, metals have low ionisation energies and low electronegativity values.
  • Hence the metallic character of the elements is greatest in the bottom left-hand corner of the periodic table.
Non-metals

Non-metals

  • On the other hand, non-metals have high ionisation energies and high electronegativities.
  • The most electronegative element in the periodic table is fluorine.
Covalent or ionic oxides

Covalent or ionic oxides

  • The variation in metallic character on going from left to right in the periodic table is also demonstrated by the change in the type of bonding of their oxides.
  • The metal oxides from Na to Al form giant ionic structures.
  • The non-metal oxides from P to Cl create molecular covalent structures.
  • Silicon, in the middle, is a metalloid, and silicon oxide is formed by a giant covalent structure.
Covalent or ionic oxides

Covalent or ionic oxides

  • The change in the type of bonding is observed by looking at the conductivity of the compounds in the molten state.
  • The metal oxides (Na to Al) conduct electricity in the molten state, whereas the non-metal oxides do not.

Acidic, Basic, and Amphoteric Oxides

Oxides change from basic through amphoteric to acidic across a period.

Basic oxides

Basic oxides

  • Metal oxides (ionic oxides) are basic and dissolve in water to produce alkaline solutions:
    • Na2O(s) + H2O(l) → 2NaOH(aq)
    • MgO(s) + H2O(l) → Mg(OH)2(aq)
  • Basic oxides neutralise acids to produce a salt and water:
    • Na2O(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l)
Acidic oxides

Acidic oxides

  • Non-metal oxides (covalent oxides) are acidic and dissolve in water to give acidic solutions.
  • Phosphorus (V) oxide gives phosphoric acid:
    • P4O10(s) + 6H2O(l) → 4H3PO4(aq)
  • Phosphorus (III) oxide gives phosphoric (III) acid:
    • P4O6(s) + 6H2O(l) → 4H3PO3(aq)
  • SO3 dissolves in water to give sulphuric (VI) acid:
    • SO3(g) + H2O(l) → H2SO4(aq)
  • SO2 dissolves in water to give sulphuric (IV) acid:
    • SO2(g) + H2O(l) → H2SO3(aq)
Amphoteric oxides

Amphoteric oxides

  • In the middle of the period, the oxides are amphoteric, meaning they can behave as both acids and bases.
  • An example of an amphoteric oxide is aluminium oxide, which is insoluble in water. Aluminium oxide will neutralise both acids and bases:
  • Neutralising sulphuric acid:
    • Al2O3(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2O(l)
  • Neutralising sodium hydroxide:
    • Al2O3(s) + 3H2O(l) + 2NaOH (aq) → 2[NaAl(OH)4](aq)
Jump to other topics
1

Structure - Models of the Particulate of Matter

2

Structure - Models of Bonding & Structure

3

Structure - Classification of Matter

3.1

The Periodic Table: Classification of Elements

3.2

Periodic Trends

3.3

Group 1 Alkali Metals

3.4

Halogens

3.5

Noble gases, group 18

3.6

Functional Groups: Classification of Organic

3.7

Functional Group Chemistry

3.8

Alkanes

3.9

Alcohols

3.10

Halogenoalkanes

4

Reactivity - What Drives Chemical Reaction?

5

Reactivity - How Much, How Fast & How Far?

6

Reactivity - The Mechanisms of Chemical Change

7

Measurement, Data Processing & Analysis

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