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Unformatted text preview: Revision Summary: Trends in the Periodic Table 2 Before working through this Factsheet you should: Be familiar with the organisation, layout and information available from the Periodic Table; Be familiar with the trends in properties such as atomic radius, ionisation energy etc (covered in Factsheet 68). After working through this Factsheet you will have revised: Trends in the chemical properties of Period 3 and Groups 1, 2 and 7, together with their explanations. Note that the chemical reactions depend on the trends on physical properties (Factsheet 69) so you should revise these first before attempting to learn the material covered here. Reactions of Period 3 elements with oxygen, chlorine and water C hem F actsheet Element Reaction with oxygen Reaction with water Reaction with chlorine Sodium Burns to form mixture of peroxide and oxide Reacts very vigorously to form the hydroxide Reacts vigorously 2Na + O 2 Na 2 O 2 and 4Na + O 2 2Na 2 O 2Na + 2H 2 O 2NaOH + H 2 2Na + Cl 2 2NaCl Magnesium Burns in air Reacts with steam to form the oxide Reacts readily 2Mg + O 2 2MgO (or hydroxide with excess steam) Mg + Cl 2 MgCl 2 Mg + H 2 O MgO + H 2 Mg + 2H 2 O Mg(OH) 2 + H 2 Aluminium Does not normally react readily with air, Reacts with steam to form the oxide Reacts readily due to surface layer of oxide. Burns in oxygen . 2Al + 3H 2 O(g) Al 2 O 3 + 3H 2 2Al +3Cl 2 2 AlCl 3 4Al + 3O 2 2Al 2 O 3 Silicon Thin oxide coating prevents reaction with air No reaction Reacts vigorously unless very high temperatures used. Si + 2Cl 2 SiCl 4 Si + O 2 SiO 2 Phosphorus White phosphorus spontaenously ignites in air, No reaction Reacts vigorously P 4 + 5O 2 P 4 O 10 2P + 3Cl 2 2PCl 3 Sulphur Burns in air . No reaction Reacts on heating S 8 + 8O 2 8SO 3 S 8 + 4Cl 2 4S 2 Cl 2 Chlorine Does not react with oxygen Reacts with water to form chlorate (I) ions N/A (although oxides do exist) Cl 2 (g) + H 2 O(l) OCl (aq) + 2H + (aq) + Cl (aq) Argon No reaction No reaction No reaction 1 Oxides - key points The enthalpy of formation of the oxides is usually negative , so the oxides are generally very stable. This is due to the high electronegativity of oxygen. Moving across the period, electronegativity increases- so the electronegativity difference with oxygen decreases. This results in reduced stability and increasing covalent character. We also see a change from basic to acidic oxides. Chlorides - key points As with oxygen, we see a decline in stability going across the period; again, this is due to the decreasing electronegativity difference. Likewise, the bonding becomes increasingly covalent. Reactions with water - key points When metals react, the products are basic....
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