2.3 group 1 - the alkali metals
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Alkali metals def
Elements in group 1 of the periodic table
Why do alkali metals have to be stored in oil?
To stop them reacting with oxygen in the air or water vapour
Does reactivity increase or decrease going down the group
Increase
What are the physical properties of alkali metals?
• Very low density compared to other metals. Lithium, sodium and potassium can float on water • Soft and and be cut with a knife • Shiny surface when cut • In a jar of oxygen has, hot alkali metals burn vigorously, forming a white smoke of their oxides
Why does the alkali metal quickly go dull after it’s been cut?
Because it’s reacting with oxygen and a layer of oxide forms on the surface
Why are group 1 elements so reactive?
Because they only need to lose 1 electron in their outermost shell to get the stable electronic structure of a noble gas
How do group 1 elements react with non-metals?
They form a metal ion carrying a 1+ charge. They always from ionic compounds
Do melting and boiling points increase or decrease going down group 1?
Decrease
Why do chemical reactions get more and more vigorous going down the group?
Because it becomes easier to lose the single electron in the outer shell to form ions with a 1+ charge
why do the melting and boiling points decrease going down group 1?
decreasing attractive forces between the outer electrons and positive ions
why do alkali metals get more reactive going down the groiup
• as you go down the group, the number of shells of electrons increases by 1 • 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
reaction of lithium with water observations
• relatively slow reaction • fizzing • lithium moves on the surface of the water
reaction of lithium with water word and symbol equation
lithium + water –> lithium hydroxide + hydrogen 2Li (s) + 2H2O (l) → 2LiOH (aq) + H2 (g)
reaction of sodium with water observations
• more vigorous fizzing • moves rapidly on the surface of the water • dissolves quickly
word and symbol equation for reaction of sodium with water
sodium + water –> sodium hydroxide + hydrogen 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)
reaction of potassium with water observations
• reacts more vigorously than sodium • burns with a lilac flame • moves very rapidly on the surface • dissolves very quickly
reaction of potassium with water word and symbol equation
potassium + water –> potassium hydroxide + hydrogen 2K(s) + 2H2O(l) –> 2KOH(aq) + H2(g)
what kind of solutions do group 1 metals produce when they react with water
alkaline solutions (metal hydroxides)
reaction of lithium with oxygen word and symbol equation
lithium + oxygen → lithium oxide 4Li (s) + O2 (g) → 2Li2O (s)
reaction of sodium with oxygen word and symbol equation
sodium + oxygen → sodium oxide 4Na (s) + O2 (g) → 2Na2O (s)
reaction of potassium with oxygen word and symbol equation
potassium + oxygen → potassium oxide 4K (s) + O2 (g) → 2K2O (s)
what do alkali metals produce when reacting with oxygen
metal oxides
what do all group 1 metals produce when reacting with chlorine
metal chlorides
lithium reaction with chlorine word and symbol equation
lithium + chlorine → lithium chloride 2Li (s) + Cl2 (g) → 2LiCl (s)