topic 6 periodic table groups Flashcards
why does group 1 have similar chemical properties
one outer electron so they have similar chemical properties
physical properties of group 1
low melting points and boiling points
very soft
alkali metals form what
ionic compounds. they lose their single outer electron so easily that sharing can’t happen, so they dont form covalent bonds
when and why does reactivity increase in group 1
as you go down the periodic table, reactivity increases as the outer electron is more easily lost as it’s further from the nucleus so it’s less strongly attracted to the nucleus and less energy is needed to remove it
group 1 reactions with cold water
react vigorously
reaction produces a hydrogen gas and a hydroxide of the metal (an alkali)
sodium + water balanced equation
2Na + 2H2O -> 2NaOH + H2
what happens when hydrogen is present
squeaky pop
describe each of the alkali metals with water
lithium will move around the surface, fizzing furiously
sodium and potassium do the same, but also melt in the heat of the reaction
potassium gets hot enough to ignite a lilac flame from the hydrogen gas being produced
why do group 7 elements have similar chemical properties
all have 7 electrons in their outer shell
the halogens exist as what?
diatomic molecules e.g. Cl2 Bl2 I2
what happens as you go down group 7?
the melting points and boiling points of the halogens increase. this means that at room temperature:
chlorine is a fairly reactive, poisonous green gas
bromine is a red brown liquid which gives off an orange vapour
iodine is a dark grey crystalline solid which gives off purple vapour
what bond is group 7 halogens
covalent bond as they share an electron to gain a full outer shell
how to predict properties of halogens further down group 7
melting points increase down the group
colours of halogens get darker down the group
so astatine (below iodine) would be a dark coloured solid at room temperature
how to test for chlorine
damp blue litmus paper over the chlorine gas
chlorine will bleach the litmus paper, turning it white. it may also turn red for a moment (it’s acidic)
why do elements become less reactive as you go down group 7?
harder to attract the extra electron to fill the outer shell when it’s further away from the nucleus
what are metal halides
when halogens react with metals to form salts
example of metal halide reaction
2Na + Cl2 -> 2NaCl
example of hydrogen halide reaction
H2 + Cl2 -> 2HCl
properties of hydrogen halides
soluble and can dissolve in water to form acidic solutions
HCl is hydrochloric acid in water
what are halogen displacement reactions called
redox reactions
why does the solution go orange when chlorine displaces bromine
the bromide ions are oxidised to bromine which turns the solution orange
halogen displacement reaction example (they all follow the same pattern)
balanced: Cl2 + 2KBr —> Br2 + 2KCl
ionic equation: Cl2 + 2Br- —> Br2 + 2Cl-
what colour solution is formed when chlorine and bromine displace iodine
brown solution
halogen displacement reactions
chlorine displaces both bromine and iodine from salt solutions
bromine can’t displace chlorine, but it does displace iodine
iodine can’t displace chlorine or bromine
this shows a reactivity trend
we can predict that astatine, below iodine, would not displace iodine.
what colour are group 0 elements at room temp
colourless
what are the noble gases
inert and monatomic (made up of single atoms not molecules)
do noble gases catch fire easily?
no
what can noble gases be used for
an inert atmosphere
argon does this in filament lamps since it’s non flammable, it stops the hot filament from burning away
flash photography used halogens to stop the flash filament from burning up during high temperature flashes
argon and helium can protect metals being welded as the inert atmosphere stops the hot metal reacting with oxygen
helium is used in airships and party balloons due to its lower density than air which causes them to float. its non flammable which is safer than hydrogen gas
what happens when you go down group 0
boiling point, melting point and density all increase
