1. Who are the Alkali Metals? List the 6 members of the Alkali Metals

2. Where are the alkali metals? The elements in group 1, on the left of the periodic table, are called the alkali metals. These metals are all very reactive and are rarely found in nature in their elemental form. lithium sodium potassium rubidium caesium francium Fr Cs Rb K Na Li

3. Why are they called the ‘alkali metals’? The alkali metals are so reactive that, as elements, they have to be stored in oil. This stops them reacting with oxygen in the air. The elements in group 1 also react with water and form alkaline compounds. This is why they are called alkali metals. Alkali metals are soft enough to be cut with a knife, and the most common alkali metals, lithium, sodium and potassium, all float on water.

4. What are the properties of the alkali metals? The characteristic properties of the alkali metals are: They are shiny. This is only seen when alkali metals are freshly cut. They are good conductors of heat and electricity. They are soft and can be cut by a knife. Softness increases going down the group. They have a low density. Lithium, sodium and potassium float on water. They have low melting and boiling points. These properties mean that the alkali metals are different to typical metals. However, alkali metals do also share some properties with typical metals:

5. What are the trends in density?

6. What is the trend in density? The alkali metals generally become more dense going down the group, but the trend is not perfect because potassium is less dense than sodium. Water has a density of 1 g/dm 3. ElementDensity (g/dm 3 ) lithium potassium sodium rubidium caesium 0.53 0.97 0.86 1.53 1.87 Which elements in group 1 will float on water?

7. What are the trends in melting point?

8. What are the trends in boiling point?

9. What is the trend in melting and boiling points? The melting points and boiling points of alkali metals decrease going down the group. The melting and boiling points decrease going down group 1 because the atoms get larger. Melting points are lower than for typical, transition, metals, because alkali metals only have 1 electron in their outer shell. Not much heat energy is needed for this electron to be lost. ElementMelting point (°C) lithium potassium sodium rubidium caesium 181 98 64 39 28 Boiling point (°C) 1342 883 760 686 671

10. Electron structure All alkali metals have 1 electron in their outer shell. This means that: lithium 2,1 sodium 2,8,1 potassium 2,8,8,1 They can easily obtain a full outer shell by losing 1 electron. They have similar physical and chemical properties. They all lose their outer shell electron in reactions to form positive ions with a +1 charge.

11. Electron structure and reactivity The reactivity of alkali metals increases down the group. What is the reason for this? CsRbKNaLi increase in reactivity The size of the element’s atoms, and the number of full electron shells, increases down the group. This means that, down the group, the electron in the outer shell gets further away from the nucleus and is shielded by more electron shells. The further away an electron is from the positive attraction of the nucleus, the easier it can be lost in reactions. This means that reactivity increases with the size of the atom.

12. Reactions of Group I elements

13. How do the alkali metals react with oxygen? All alkali metals react with oxygen in the air to form metal oxides. This produces a layer of dull oxide on the surface of the metal, called tarnish. The speed with which alkali metals react with oxygen in the air increases going down the group: Why are alkali metals stored in oil? lithium – tarnishes slowly sodium – tarnishes quickly potassium – tarnishes very quickly. The oil prevents them from reacting with oxygen and tarnishing.

14. What are the word and chemical equations for the reaction that causes sodium to tarnish? What is the equation for the reaction with oxygen? The reaction between an alkali metal and oxygen is an example of an oxidation reaction: alkali metal + oxygen  alkali metal oxide 4Na (s) + O 2 (g)  2Na 2 O (s) sodium + oxygen  sodium oxide The word and chemical equations for the reaction between lithium and oxygen are: 4Li (s) + O 2 (g)  2Li 2 O (s) lithium + oxygen  lithium oxide

15. All the alkali metals react vigorously with water. The reaction produces a gas that ignites a lighted splint with a squeaky pop. What is this gas? What does the reaction with water produce? It is an exothermic reaction as it releases a lot of heat. When green universal indicator is added to the reaction mixture, it turns purple. What does this tell you about the products of this reaction? The reaction with water becomes more vigorous as you go down the group.

16. 2M(s) + 2H 2 O(l)  2MOH (aq) + H 2 (g) alkali metal + water  alkali metal + hydrogen hydroxide This reaction creates alkaline hydroxide ions. The general equation for the reaction between an alkali metal reacting with water is: What is the equation for the reaction with water? This is why the group 1 elements are called the alkali metals.

17. How does lithium react with water? Lithium is the least reactive of the alkali metals. 2Li (s) + 2H 2 O (l)  2LiOH (aq) + H 2 (g) lithium + water  lithium + hydrogen hydroxide When added to water, it fizzes and moves around slowly across the surface of the water. What is the equation for this reaction?

18. How does sodium react with water? When added to water, sodium fizzes more than lithium, and moves quickly across the surface of the water. 2Na (s) + 2H 2 O (l)  2NaOH (aq) + H 2 (g) sodium + water  sodium + hydrogen hydroxide What is the equation for this reaction? The hydrogen sometimes catches fire because of the heat from the reaction. The sodium melts as it reacts, and it becomes spherical and shiny, like a ball bearing.

19. How does potassium react with water? When added to water, the potassium moves across the surface of the water very quickly. 2K (s) + 2H 2 O (l)  2KOH (aq) + H 2 (g) potassium + water  potassium + hydrogen hydroxide What is the equation for this reaction? Like sodium, it melts with the heat of the reaction. The reaction produces so much heat that the hydrogen given off catches alight. What colour would the flame be?

20. All the alkali metals react vigorously with water. The reaction produces a gas that ignites a lighted splint with a squeaky pop. What is this gas? Reactions with water produce It is an exothermic reaction as it releases a lot of heat. When green universal indicator is added to the reaction mixture, it turns purple. What does this tell you about the products of this reaction? The reaction with water becomes more vigorous as you go down the group.

21. 2M(s) + 2H 2 O(l)  2MOH (aq) + H 2 (g) alkali metal + water  alkali metal + hydrogen hydroxide This reaction creates alkaline hydroxide ions. The general equation for the reaction between an alkali metal reacting with water is: What is the equation for the reaction with water? This is why the group 1 elements are called the alkali metals.

22. How does lithium react with water? Lithium is the least reactive of the alkali metals. 2Li (s) + 2H 2 O (l)  2LiOH (aq) + H 2 (g) lithium + water  lithium + hydrogen hydroxide When added to water, it fizzes and moves around slowly across the surface of the water. What is the equation for this reaction?

23. How does sodium react with water? When added to water, sodium fizzes more than lithium, and moves quickly across the surface of the water. 2Na (s) + 2H 2 O (l)  2NaOH (aq) + H 2 (g) sodium + water  sodium + hydrogen hydroxide What is the equation for this reaction? The hydrogen sometimes catches fire because of the heat from the reaction. The sodium melts as it reacts, and it becomes spherical and shiny, like a ball bearing.

24. How does potassium react with water? When added to water, the potassium moves across the surface of the water very quickly. 2K (s) + 2H 2 O (l)  2KOH (aq) + H 2 (g) potassium + water  potassium + hydrogen hydroxide What is the equation for this reaction? Like sodium, it melts with the heat of the reaction. The reaction produces so much heat that the hydrogen given off catches alight. What colour would the flame be?

25. Task  Watch and learn But what about caesium and rubidium?

26. Alkali metals burst into flames when heated and added to chlorine. They form metal chlorides. How do alkali metals react with chlorine? 2Li (s) + Cl 2 (g)  2LiCl (s) lithium + chlorine  lithium chloride What are the word and chemical equations for the reaction that produces sodium chloride? 2Na (s) + Cl 2 (g)  2NaCl (s) sodium + chlorine  sodium chloride alkali metal + chlorine  alkali metal chloride The word and chemical equations for the reaction between lithium and chlorine are: