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The period 3 elements

The period 3 elements. The eight period 3 elements are found in the third row of the periodic table. 1. 2. 3. 4. 5. 6. 7. Physical properties of period 3. What properties?. Reactions with water. Reactions with water: summary. Element. Description. Equation. Na. Mg. Al. Si. P.

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The period 3 elements

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  1. The period 3 elements The eight period 3 elements are found in the third row of the periodic table. 1 2 3 4 5 6 7

  2. Physical properties of period 3

  3. What properties?

  4. Reactions with water

  5. Reactions with water: summary Element Description Equation Na Mg Al Si P S Cl Cl2(aq) + H2O(l) HClO(aq) + HCl(aq) Ar vigorous 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g) Mg(s) + H2O(g) → MgO(s) + H2(g) slow with cold water;vigorous with steam no reaction – no reaction – no reaction – no reaction – dissolves to formchlorine water no reaction –

  6. Reactions with water: redox 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) Mg(s) + H2O(g) → MgO(s) + H2(g) Cl2(aq) + H2O(l) HClO(aq) + HCl(aq) The reactions with water are all redox reactions. 0 +1 -2 +1 -2 +1 0 0 +1 -2 +2 -2 0 0 +1 -2 +1 +1 -2 +1 -1 The metals are oxidised and their oxidation state increases. The hydrogen is reduced and its oxidation state decreases. The chlorine is both oxidized and reduced.

  7. Reactions with oxygen

  8. Reactions with oxygen: summary Element Description Equation Na Mg Al Si P S burns vigorously with a yellow flame 4Na(s) + O2(g) → 2Na2O(s) burns vigorously with a bright white flame 2Mg(s) + O2(g) → 2MgO(s) burns vigorously with a bright white flame 4Al(s) + 3O2(g) → 2Al2O3(s) burns with a bright white flame and white smoke Si(s) + O2(g) → SiO2(s) burns spontaneously with a bright white flame and smoke 4P(s) + 5O2(g) → P4O10(s) burns with a blue flame S(s) + O2(g) → SO2(g)

  9. Reactions with oxygen: redox 4Na(s) + O2(g) → 2Na2O(s) The reactions of the period 3 elements with oxygen are redox reactions. In each reaction, the oxidation state of the elements increases and the oxidation state of the oxygen decreases. For example, when sodium is burned in oxygen the oxidation state of the sodium increases from 0 to +1 (oxidation), while the oxidation state of the oxygen decreases from 0 to -2 (reduction). 0 0 +1 -2

  10. What’s the oxidation number?

  11. Reactions: summary

  12. Properties of period 3 oxides

  13. Reaction of period 3 oxides with water

  14. Reaction of sulfur oxides with water

  15. Period 3 oxides and water: summary Oxide Bonding Ions presentafter reaction Type of solution pH Na2O MgO Al2O3 SiO2 P4O10 SO2 SO3 ionic Na+(aq),OH-(aq) strongly alkaline 13–14 Mg2+(aq),OH-(aq) moderately alkaline 10 ionic ionic/covalent – (insoluble) – 7 – 7 covalent – (insoluble) covalent H+(aq),H2PO4-(aq) strongly acidic 0–1 covalent H+(aq),HSO3-(aq) weakly acidic 2–3 H+(aq),HSO4-(aq) strongly acidic 0–1 covalent

  16. Alkaline oxides Na2O(s) + H2O(l) → 2Na+(aq) + 2OH-(aq) MgO(s) + H2O(l) → Mg2+(aq) + 2OH-(aq) The reaction of period 3 oxides with water can be explained by examining their bonding and structure. Sodium and magnesium oxides are ionic compounds. They both contain the oxide ion (O2-), which is a very strong base. It reacts readily with water to produce hydroxide ions (OH-) and a strongly alkaline solution. Magnesium oxide produces a less alkaline solution than sodium oxide due to its lower solubility.

  17. Insoluble oxides Aluminium oxide is an ionic compound but the bonds between aluminium and oxygen ions display some covalent character. This is because the difference in electronegativity between aluminium (1.6) and oxygen (3.4) is less than for sodium (0.9) and magnesium (1.3). Silicon dioxide is a giant macromolecule, with its atoms covalently bonded together. Both these oxides are insoluble in water.

  18. Acidic oxides P4O10(s) + 6H2O(l) → 4H3PO4(aq) 4H+(aq) + 4H2PO4-(aq) SO2(g) + H2O(l) → H2SO3(aq) H+(aq) + HSO3-(aq) SO3(s) + H2O(l) → H2SO4(aq) H+(aq) + HSO4-(aq) Phosphorus oxides and sulfur oxides are covalent molecules and react with water to form acidic solutions: The general trend is that oxides change from alkaline to acidic across period 3.

  19. pH of period 3 oxide solutions

  20. Period 3 oxides and water: true or false?

  21. Reaction with acids: Na2O, MgO Na2O(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) MgO(s) + H2SO4(aq) → MgSO4(aq) + H2O(l) Both sodium oxide and magnesium oxide react with acids to produce salt and water. For example: Sodium oxide reacts with hydrochloric acid to produce sodium chloride: Magnesium oxide reacts with sulfuric acid to produce magnesium sulfate:

  22. Reaction with acids and bases: Al2O3 Al2O3(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3H2O(l) Al2O3(s) + 2NaOH(aq) + 3H2O(l) → 2NaAl(OH)4(aq) Aluminium oxide reacts with both acids and bases. It is anamphotericoxide. For example: Aluminium oxide reacts with sulfuric acid to produce aluminium sulfate: Aluminium oxide reacts with hot concentrated sodium hydroxide to produce sodium aluminate:

  23. Reaction with bases: SiO2 SiO2(s) + 2NaOH(aq) → Na2SiO3(aq) + H2O(l) Silicon dioxide reacts as a weak acid with strong bases. For example, it reacts with hot concentrated sodium hydroxide to produce sodium silicate:

  24. Reaction with bases: P4O10 H3PO4(aq) + NaOH(aq) → NaH2PO4(aq) + H2O(l) NaH2PO4(aq) + NaOH(aq) → Na2HPO4(aq) + H2O(l) Na2HPO4(aq) + NaOH(aq) → Na3PO4(aq) + H2O(l) 3NaOH(aq) + H3PO4(aq) → Na3PO4(aq) + 3H2O(l) The reaction of phosphorus(V) oxide with alkalis is really the reaction of phosphoric(V) acid, formed in a reaction with water. Phosphoric(V) acid is tribasic – it can donate 3H+ ions – so the reaction with sodium hydroxide has three steps: The overall reaction is:

  25. Reaction with bases: SO2 SO2(aq) + NaOH(aq) → NaHSO3(aq) NaHSO3(aq) + NaOH(aq) → Na2SO3(aq) + H2O(l) Sulphur dioxide reacts with sodium hydroxide to first produce sodium hydrogensulfate(IV): A further reaction occurs to produce sodium sulfate(IV): The overall pattern is that the basic metal oxides react with acids to form salts and the acidic non-metal oxides react with bases to form salts. The oxides of elements in the middle of the period are amphoteric and show both acidic and basic properties.

  26. Reaction with acids and bases

  27. Glossary

  28. What’s the keyword?

  29. Period 3 trends: summary

  30. Multiple-choice quiz

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