Periodic table Flashcards
what do elements in the same group have ?
same no. of electrons in outer shell — similar chemical properties
define first ionisation energy
energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms
what type of reaction is ionisation energy reactions ?
endothermic - energy needed to ionise an atom
what are the 3 factors of ionisation energy ?
- nuclear charge
- atomic radius
- shielding (greatest factor)
what causes high ionisation energy ?
strong attraction between electron and nucleus, so more energy is needed to overcome the attraction and remove the electron
ionisation energy … down a group
decreases
why does ionisation energy increase across a period ?
positive charge of nucleus increases (no. of protons increases) which pulls electrons closer, decreasing atomic radius
why is there a ionisation energy drop between group 2 and 3 ?
- group 3 elements go in p orbitals, which are found further from nucleus than s orbitals (larger atomic radius)
- s electrons provide some shielding
why is there a ionisation energy drop between group 5 and 6 ?
- in group 6, electron being removed from orbital with two electrons
- repulsion between two electrons makes it easier to remove an electron
what is an allotrope ?
element that has different forms (in the same state)
what is the shape of the molecules in diamond ?
tetrahedral (carbon bonded to 4 other carbons)
what does sublime mean ?
change from solid straight to gas (no liquid phase)
why is diamond a good thermal conductor ?
vibrations travel easily through the stiff lattice
what specific structure does diamond have ?
crystal lattice structure
what structure does silicon have similar to ?
diamond
what causes graphite to be a good lubricant ?
arranged in layers, with weak H-bonds between them (easily broken), so sheets can slide over each other
how can graphite conduct electricity ?
has delocalised electrons which are free to move and can carry charge - electric current can flow
why is graphite less dense than diamond ?
layers are quite far apart compared to length of covalent bonds
why does graphite have a high melting point ?
strong covalent bonds in hexagonal sheets
why is graphene known as the best conductor ?
delocalised electrons / as well as it being 2D, so electrons can move quickly above / below sheet
what else do the delocalised electrons in graphene do ?
strengthen covalent bonds between carbon atoms (making it strong)
a single layer of graphene is …
transparent and light
what structure do metals exist as ?
giant metallic lattice structures
what is metallic bonding ?
electrostatic attraction between metal cations and (sea of) delocalised electrons
how are metals malleable / ductile ?
no specific bonds holding ions together, so can slide past each other
what affects metal melting points ?
- no. of delocalised electrons per atom
- site of metal ion
why are metals good thermal conductors ?
delocalised electrons can pass kinetic energy to each other
what is group 2 known as ?
alkali earth metals
group 2 metal + water =
metal hydroxide + hydrogen
group 2 metal burnt in (+) oxygen =
solid white metal oxide
group 2 metal + water =
dissolved metal hydroxide (OH- ions make really alkaline)
what is the use for calcium hydroxide ?
agriculture to neutralise acidic soil
what is the use for magnesium hydroxide / calcium carbonate ?
indigestion tablets as antacids
give state and colour of fluorine
pale yellow gas
give state and colour of chlorine
green gas
give state and colour of bromine
red-brown liquid
give state and colour of iodine
grey solid
what is another way of saying that halogens get less reactive down the group ?
they become less oxidising
what is the test for halides ?
- add dilute nitric acid (remove ions)
- add silver nitrate solution
- silver halide precipitate formed
in the halide test, what colour precipitate does chlorine give ?
white
in the halide test, what colour precipitate does bromine give ?
cream
in the halide test, what colour precipitate does iodine give ?
yellow
for Cl, Br, I, describe with ammonia solution
Cl - dissolve in dilute
Br - dissolves in conc
I - insoluble in conc
what is a disproportionate reaction ?
reaction where a molecule is both oxidised and reduced
what type of reaction do halogens undergo with alkalis ?
disproportionate reaction
what do you get if you react chlorine with sodium hydroxide ?
bleach (NaClO) (disproportionation)
give the uses of bleach
water treatment / paper and textiles
how is bacteria killed in water ?
- chlorine mixed with water
- HCl + chloric(I) acid as products
- chloric acid ionises, making chlorate ions
- chlorate ions kill bacteria
what (two) types of reaction is chlorine + water ?
disproportionation and reversible
what is the test for carbonates ?
- add dilute HCl
- carbon dioxide will be released
- test for CO2 using limewater (turn cloudy)
what is the test for sulfates ?
- add dilute HCl
- add barium chloride solution
- white precipitate of barium sulfate
what is test for ammonia gas ?
damp piece of red litmus paper will turn blue
what is test for ammonium ions ?
- add NaOH
- warm mixture
- ammonia gas will be given off
state colour of chlorine:
RTP -
(aq) -
dissolved in hexane -
RTP - green
(aq) - colourless
dissolved in hexane - colourless
state colour of bromine:
RTP -
(aq) -
dissolved in hexane -
RTP - brown
(aq) - orange
dissolved in hexane - orange
state colour of iodine:
RTP -
(aq) -
dissolved in hexane -
RTP - grey/black
(aq) - brown
dissolved in hexane - purple
