Edexcel IGCSE Chemistry Group 1 Alkali Metals PDF

Head to www.savemyexams.com for more awesome resources Edexcel IGCSE Chemistry Your notes Group 1 (Alkali Metals) Contents Group 1 (Alkali Metals) Group 1: Reactivity & Electronic Configurations...

Head to www.savemyexams.com for more awesome resources Edexcel IGCSE Chemistry Your notes Group 1 (Alkali Metals) Contents Group 1 (Alkali Metals) Group 1: Reactivity & Electronic Configurations Page 1 of 7 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Group 1 (Alkali Metals) Your notes Group 1 elements The Group 1 metals are known as the alkali metals They form alkaline solutions when they react with water The Group 1 metals are lithium, sodium, potassium, rubidium, caesium and francium and they are found in the first column of the periodic table The alkali metals share similar characteristic chemical properties because they each have one electron in their outermost shell Some of these properties are: They are all soft metals which can easily be cut with a knife They have relatively low densities and low melting points They are very reactive (they only need to lose one electron to become highly stable) Group 1 elements in the Periodic Table The alkali metals lie on the far left of the periodic table, in the very first group Reaction with water The reaction of the Group 1 metals with water provides evidence for categorising these elements into the same chemical family The general pattern shown is: Group 1 metal + water ⟶ metal hydroxide + hydrogen Page 2 of 7 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources 2M (s) + 2H2O (l) ⟶ 2MOH (aq) + H2 (g) where M is Li, Na, K, Rb or Cs Your notes The hydroxides formed all have the same general formula and are colourless, aqueous solutions The metals are so named because they form alkalis in water Examiner Tip Remember the Group 1 metals all produce alkaline solutions (>pH 7) when they react with water. Lithium will produce a solution of lithium hydroxide; sodium will produce a solution of sodium hydroxide and so on. Make sure you can give the reaction equations with the correct state symbols to show what is happening during the reactions! Page 3 of 7 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Trends in Group 1 The differences between the reactions of the group 1 metals with water and oxygen provide evidence Your notes of trends within the group Reactions with water The reactions of the alkali metals with water get more vigorous as you descend the group Summary of the reactions of the first three alkali metals with water Element Reaction Observations lithium + water → lithium hydroxide + hydrogen Relatively slow reaction Fizzing Li 2Li (s) + 2H2O (l) → 2LiOH (aq) + H2 (g) Lithium moves on the surface of the water sodium + water → sodium hydroxide + hydrogen More vigorous fizzing Moves rapidly on the surface Na 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g) of the water Dissolves quickly Reacts more vigorously than potassium + water → potassium hydroxide + sodium hydrogen Burns with a lilac flame K Moves very rapidly on the 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) surface Dissolves very quickly Reactions with oxygen The alkali metals react with oxygen in the air forming metal oxides, which is why the alkali metals tarnish when exposed to the air The metal oxide produced is a dull coating which covers the surface of the metal The metal tarnish more rapidly as you go down the group Summary of the reactions of the first three alkali metals with oxygen Element Reaction lithium + oxygen → lithium oxide Li 4Li (s) + O2 (g) → 2Li2O (s) sodium + oxygen → sodium oxide Na 4Na (s) + O2 (g) → 2Na2O (s) Page 4 of 7 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources potassium + oxygen → potassium oxide K 4K (s) + O2 (g) → 2K2O (s) Your notes Physical trends Apart from the chemical trends there are also patterns to be seen in the physical properties The alkali metals are soft and easy to cut, getting softer as you move down the group The first three alkali metals are less dense than water They all have relatively low melting points which decrease as you move down the group, due to decreasing attractive forces between outer electrons and positive ions Graph to show the physical trends in Group 1 The melting point of the Group 1 metals decreases as you descend the group Examiner Tip Trends are patterns of behaviour that change as you go down a group or across a period. Trends are not the same as rules, so sometimes there are odd properties that seem inconsistent, but the overall patterns remain the same. Page 5 of 7 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Predicting properties in Group 1 Following these trends, we can say that: Your notes Rubidium, caesium and francium will react even more vigorously with air and water than the first three alkali metals Of the alkali metals, lithium is the least reactive (as it is at the top of Group 1) and francium would be the most reactive (as it’s at the bottom of Group 1) Using the information given in the trends we would predict that rubidium: would be a soft grey solid appears shiny when freshly cut is more dense than potassium (> 0.86 g cm-3) has a lower melting point than potassium (< 63.5 oC) Examiner Tip You could be asked to make predictions about how rubidium would be expected to react with water, knowing that it lies below potassium in group 1. Words like 'explosively' and 'violently' would be good ones to choose when describing the reaction. Page 6 of 7 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Group 1: Reactivity & Electronic Configurations Your notes Electronic configuration of Group 1 elements The reactivity of the Group 1 metals increases as you go down the group When a Group 1 element reacts its atoms only need to lose electron, as there is only 1 electron in the outer shell When this happens, 1+ ions are formed The next shell down automatically becomes the outermost shell and since it is already full, a Group 1 ion obtains noble gas configuration As you go down Group 1, the number of shells of electrons increases by 1 This means that the outermost electron gets further away from the nucleus, so there are weaker forces of attraction between the outermost electron and the nucleus Less energy is required to overcome the force of attraction as it gets weaker, so the outer electron is lost more easily So, the alkali metals get more reactive as you descend the group Electronic configuration of Group 1 elements These electron shell diagrams of the first 3 alkali metals show that the Group 1 metals have 1 electron in their outer shell Examiner Tip In your exams, you could be asked to explain the trend in reactivity of the alkali metals - make sure you answer this question using their electronic configuration to support your answer. 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