5 Chemistry - The Periodic Table
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where are the alkali metals found?
group 1
what happens when alkali metals are added to water?
they react forming hydrogen gas
how do you test for hydrogen?
you place a burning splint in the test tube and it makes a squeaky noise if hydrogen is present
as you go down the periodic table what happens to the reactivity of the alkali metals?
it increases
what is general word equation for an alkali metal reacting with water? give a balanced symbol equation
metal + water –> metal hydroxide + hydrogen sodium + water –> sodium hydroxide + hydrogen 2Na + 2H20 –> 2NaOH (aq) + H2
where are the halogens found?
group 7
why are halogens always in “two’s” ?
because they are diatomic, they need only one electron to fill the valence shell
as you go down the periodic table (increase atomic mass), what happens to reactivity of halogens?
it gets less reactive
halogens are able to displace which other halogens
the ones that are below it on the periodic table
what are displacement equations?
Cl2 + 2KBr –> 2KCl + Br2
what are properties of halogens?
form coloured gases are poisonous dont conduct electricity form diatomic molecules
what are properties of alkali metals?
good conductors of heat and electricity softer/lighter than most metals low density low melting/boiling points
what are properties of transition metals?
ductile (drawn into wires) malleable (hammered into shapes) good conductors of heat / electricity valence electrons present in more than one shell several oxidation states high density and melting points
what are catalysts?
transition metals that are used to speed up reactions
what is found in group 0?
noble gases
why are they called noble gases?
because they are INERT (very unreactive)
why are noble gases inert?
because they have full electron valence shells so no reacting is needed because they are already stable with full shells
what are uses for noble gases
very safe because they are inert glow when a current passes through them at low pressure fill balloons, airships, protect metals being welded, advertising signs, lasers, lamps
what does the period in the periodic table show?
number of electron shells
what does the group number show?
how many electrons in the outer shell