3.2.4

Period 3 Elements & Oxides

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Reactions of the Third Period with Water

The Third Period elements show many interesting reactions with water.

Reactions of Na with water

Reactions of Na with water

  • 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
    • This reaction is vigorous with cold water.
    • The solution you get is highly basic.
Reactions of Mg with water

Reactions of Mg with water

  • Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)
    • This reaction is slow with cold water.
Reactions of Mg with steam

Reactions of Mg with steam

  • Similarly, if you react magnesium with steam, you get magnesium oxide.
    • Mg(s) + H2O(g) → MgO(s) + H2(g)
    • This is a vigorous reaction and makes the Mg burn with a white light.

Reactions of the Third Period with Oxygen

The elements of the third period have distinctive and different reactions with oxygen.

Na, Mg, Al oxides

Na, Mg, Al oxides

  • The equations are:
    • 4Na(s) + O2(g) → 2Na2O(s)
    • 2Mg(s) + O2(g) → 2MgO(s)
    • 4Al(s) + 3O2(g) → 2Al2O3(s)
  • The common feature is that these metals form their normal ions: Na+, Mg2+ and Al3+.
    • To work out the equations, you just have to balance the overall charge with oxide ions.
Silicon and phosphorus oxides

Silicon and phosphorus oxides

  • These oxides are covalent materials. The reactions for their formation are:
    • Si(s) + O2(g) → SiO2(s)
    • P4(s) + 5O2(g) → P4O10(s)
  • Both of these get the oxidation state of their group:
    • Phosphorus is +5 and in group 5.
    • Silicon is +4 and in group 4.
Sulfur

Sulfur

  • Sulfur can form multiple oxides. The most common are sulfur dioxide and sulfur trioxide.
  • The equation for the formation of sulfur dioxide is:
    • S8(s) + 8O2(g) → 8SO2(g)
  • Sulfur trioxide is made from sulfur dioxide using a catalyst. The equation is:
    • 2SO2(g) + O2(g) V2O5cat.450C, 2atm\xrightarrow[{V_2O_5 \text{cat.}}]{\text{450C, 2atm}} 2SO3(g)
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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