Topic 6 - Groups in the periodic table Flashcards
(26 cards)
GROUP 1 - Explain why some elements can be classified as group 1 metals
GROUP 1 - ALKALI METALS
Same physical properties:
- good heat and electricity conductors
- shiny when freshly cut
- soft
- relatively low melting points (but solid)
GROUP 1 - explain what happens when a group 1 metal reacts with water
Produces an alkaline metal hydroxide & hydrogen
Eg:
Sodium + water —> sodium hydroxide + hydrogen
GROUP 1 - describe the reactivity of the alkali metals
REACTIVITY increases down the group:
LITHIUM - fizzes steadily
SODIUM - melts into a ball from heat released and fizzes rapidly
POTASSIUM - gives off sparks, hydrogen produced burns with a lilac-coloured flame
GROUP 1 - Explain the density and storage of the few metals
DENSITY:
Lithium, sodium, potassium less dense than water - float
STORAGE:
Lithium, sodium, potassium stored in oil - keeps air + water away
GROUP 1 - explain the pattern of reactivity in terms of electronic configuration
all have one electron in outer shell, this lost to form ions with +1 charge
easier outer electron is lost, more reactive metal
GROUP 7 - what are the colours and states of chlorine, bromine and iodine at room temp
CHLORINE - yellow/green gas
BROMINE - red/brown liquid
IODINE - dark grey (forms purple vapour when warmed) solid
GROUP 7 - describe the melting and boiling points as you go down
MELTING POINTS increase
BOILING POINTS increase
GROUP 7 - describe the bonding in simple molecular substances
when simple molecular substances melt or boil:
- weak intermolecular forces are overcome
- strong covalent bonds dont break
GROUP 7 - describe the bonding as you go down the group
- intermolecular forces between molecules stronger
- more heat energy needed to overcome forces
GROUP 7 - describe the test for chlorine
put damp blue litmus paper into container. if chlorine present then paper turns red, then is bleached white
GROUP 7 - what is formed when the halogens react with metals
halogens + metals = metal halide compounds
eg // sodium + chlorine —> sodium chloride
GROUP 7 - explain what happens in terms of ions when halogens react with metals
halogen atoms GAIN electrons and are REDUCED
ions formed:
- have 1- charge
- are called halide ions
HALIDES are compounds of metals/hydrogens with halogens
GROUP 7 - explain the electronic configuration going down the group
going down:
- outer shell gets further from nucleus
- shielding by inner electrons
- force of attraction between nucleus and outer shell electrons gets weaker
- electrons gained less easily
- elements become less reactive
GROUP 7 - explain how the electronic configuration changes when a halogen reacts with a metal/hydrogen
halogen atom - 7 electrons
when reacts, each halogen gains one electron to complete outer shell
less easily halogen gains electron, less reactive halogen is
GROUP 7 - explain what happens in a halogen displacement reaction (using chlorine and bromine as an example)
these are REDOX reactions eg when chlorine displaces bromine from bromide ions in solution
- chlorine atoms gain electrons and reduced to chloride atoms:
Cl2 (aq) + 2e- —> 2Cl- (aq) - bromide ions lose electrons and are oxidised to bromine:
2Br- (aq) —> Br2(aq) + 2e-
GROUP 7 - explain how you can demonstrate halogen displacement reactions
adding a HALOGEN solution to a METAL HALIDE solution, see if mixture darkens eg:
‘chlorine water’ displaces bromine from aqueous sodium bromide solution
Cl2 (aq) + 2NaBr(aq) —> 2NaCl (aq) + Br2 (aq)
GROUP 7 - explain how fluorine, chlorine and bromine react with hydrogen
FLUORINE - reacts explosively in dark
CHLORINE - reacts explosively in sunlight
BROMINE - reacts vigorously in a flame
GROUP 7 - explain how the hydrogen halides react with water
all dissolve in water, producing ACIDIC solutions
eg// hydrogen chloride gas HCl (g) produces hydrochloric acid HCl (aq), fully dissociates to form H+ (aq) and Cl- (aq) ions
GROUP 7 - using the reactivity of bromine, iodine and chlorine predict whether astatine will react with potassium iodide
astatine will not react with potassium iodide because:
- reactivity decreases down group 7 (astatine at bottom)
- astatine less reactive than iodine
GROUP 7 - describe which halogens displace each other when reacted with the potassium halides (chlorine, bromine, iodine reacting with chlorine, bromine, iodine)
- chlorine with bromide
- chlorine with iodide
- bromine with iodide
they all turn darker, showing a displacement reaction
GROUP 0 - explain why the noble gases are chemically inert
lack of reactivity because:
- atoms have full outer shells so
- no tendency to lose or gain electrons
GROUP 0 - explain the use of helium and properties needed
USE - lifting gas in party balloons and airships
NEEDS low density & inertness
REASONS - less dense than air so balloons and airships rise, non flammable
GROUP 0 - explain the use of argon, krypton and xenon and properties needed
USE - filling gas in filament lamps
NEEDS inertness
REASONS - metal filament becomes hot enough to glow, inert gases stop it burning away
GROUP 0 - explain the use of argon and properties needed
USE - shield gas during welding
NEEDS inertness
REASONS - denser than air, keeps air away from metal, inert so metal doesnt oxidise
