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.

Illustrative background for Reactions of Na with waterIllustrative background for Reactions of Na with water ?? "content

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.
Illustrative background for Reactions of Mg with waterIllustrative background for Reactions of Mg with water ?? "content

Reactions of Mg with water

  • Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)
    • This reaction is slow with cold water.
Illustrative background for Reactions of Mg with steamIllustrative background for Reactions of Mg with steam ?? "content

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.

Illustrative background for Na, Mg, Al oxidesIllustrative background for Na, Mg, Al oxides ?? "content

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.
Illustrative background for Silicon and phosphorus oxidesIllustrative background for Silicon and phosphorus oxides ?? "content

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.
Illustrative background for SulfurIllustrative background for Sulfur ?? "content

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

1Structure - Models of the Particulate of Matter

2Structure - Models of Bonding & Structure

3Structure - Classification of Matter

3.1The Periodic Table: Classification of Elements

3.2Periodic Trends

3.3Group 1 Alkali Metals

3.4Halogens

3.5Noble gases, group 18

3.6Functional Groups: Classification of Organic

3.7Functional Group Chemistry

3.8Alkanes

3.9Alcohols

3.10Halogenoalkanes

4Reactivity - What Drives Chemical Reaction?

5Reactivity - How Much, How Fast & How Far?

6Reactivity - The Mechanisms of Chemical Change

7Measurement, Data Processing & Analysis

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