Topic 8 - Periodic table Flashcards
what are the three groups we need to know in the periodic table?
- alkali metals
- halogens
- noble gas
what group are alkali metals in ? what are the first 3 alkali metals ?
- they are the elements in group 1
- Lithium ( Li ) , Sodium ( Na ) , Potassium ( K )
properties of alkali metals
- silvery solids that have to be stored in oil
- very soft : cut with knife
- have low MP and BP compared to other metals
- they all form 1+ ions and lose their valence electron to form ionic compounds
reactivity trend of alkali metals
- as you go DOWN group 1, the reactivity of the metal INCREASES
why do the alkali metals have this trend?
- increased atomic radius
- means increased distance between valence electron and positively charged nucleus
- weakens the attractive electrostatic force
- valence electron is removed more readily which makes it more reactive
alkali metal + water
metal hydroxide + hydrogen
metal hydroxide solutions
the hydroxides that are formed dissolve in water to give alkaline solutions and turn u.i purple
reaction of alkali metals with water
the reaction becomes more violent and vigorous as you go down the group
what group are halogens in ? what are the first 3 halogens ?
- they are elements in group 7
- Chlorine ( Cl ) , Bromine ( Br ) , Iodine ( I )
properties of halogens
- they all exist as diatomic molecules and share 1 pair of electrons through covalent bonding
what does chlorine look like at r.t
poisonous , green gas
what does bromine look like at r.t
poisonous , red-brown liquid
what does iodine look like at r.t
poisonous , dark-grey solid
gives off purple vapour when heated
physical properties of halogens
as you go DOWN the group
- melting point INCREASES
- colours of halogens becomes DARKER
test for chlorine
- use damp blue litmus paper
- it will turn from blue to white
reactivity trend of halogens
- as you go DOWN group 7, the reactivity of the metal DECREASES
why do the halogens have this trend?
- increased atomic radius
- means increased distance between valence electron and positively charged nucleus
- weakens the attractive electrostatic force
- becomes harder to attract an extra electron
halogen + metal
metal halide ( sodium chloride )
halogen + hydrogen
hydrogen halide
hydrogen halides?
they dissolve in water to form acidic solutions
displacement reactions involving halides
a more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt
redox reactions
- both reduction and oxidation happen simultaneously
- halogens are reduced ( gain electrons ) to form halide ions
- the halide ions are oxidised ( lose electrons ) to form halides
what group are noble gases in ? what are the first 3 noble gases ?
- they are in group 0
- Helium ( He ) , Neon ( Ne ) , Argon
( Ar )
electronic configuration of noble gase
- they all have full outer shell of electrons
why are noble gases inert / unreactive
- the outer shell is energetically stable
- they don’t need to give up or gain electrons to become more stable
- this means they don’t have to react with other substances
- they are also non flammable
properties of all noble gases
all colourless, monoatomic gases at r.t
why is inertness useful for a noble gas
for example argon provides an inert atmosphere in filament lamps as it is non-flammable
why is the density of noble gases useful?
- noble gases have low densities
- helium and neon are less dense than air so can be pumped into balloons to make them float
