Module 3 Flashcards
mendeleev
arranged in order of atomic mass
grouped elements with similar properties
left gaps for undiscovered elements
- predicted properties of missing elements
modern periodic table
positions linked to physical and chemical properties
increasing atomic number (L to R)
grouped atoms with same number of electrons in outer shell
periods- number of the highest energy electron shell
first ionisation energy
energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
factors affecting ionisation energy
atomic radius
nuclear charge
electron shielding
second ionisation energy
energy required to remove one electron from each ion in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
predictions from successive ionisation energy
no of electrons in outer shell
group of element in periodic table
identity of an element
metallic bonding
strong electrostatic attraction between cations and delocalised electrons
cations- fixed maintaining shape
DE- mobile and able to move throughout structure
giant metallic lattice
properties of metals
strong metallic bonds
high elec condictivity
high mp/bp
not soluble
giant covalent
billions of atoms held together by strong covalent bonds to form giant covalent lattice
giant covalent properties
high mp/bp
insoluble
non conductors (except graphene and graphite)
graphene
single layer of graphite
hexagonally arranged carbons
linked by strong covalent bonds
graphite
parallel layers of hexagonally arranged carbon atoms
layers boded by weak london forces
spare electron from each carbon atoms becomes delocalised
group 2 trends
ionisation energies decrease down group
reactivity increase down group
halogens
reactivity decreases down group
boiling point increase down group
halogen- halide displacement
colour change
water-> cyclohexane halogen solutions
I- brown-> violet
Br- orange-> paler orange
Cl- pale green-> slightly darker green
disproportionation
redox reaction
same element both oxidised and reduced
chlorine + water
for each chlorine molecule, one atom is oxidised, other is reduced
produces HClO and HCl
chlorine + cold, dilute aqueous NaOH
Cl2 + 2NaOH -> NaClO (aq) + NaCl (aq) + H2O
pros/cons of chlorine use
kills bacteria in water so it is safe to drink
respiratory irritant in small concentrations
large conc can be fatal
tests for halides
aqueous halide ions react with aqueous silver ions to form silver halide precipitate
halide test gen eq
Ag+ (aq) + X- (aq) –> AgX (s)
qualitative analysis
relies on observations not measurements
eg, gas bubbles, precipitates, colour changes, identification of gases
carbonate test
react with acids to form CO2
add dilute nitric acid to solid/ solution, see if theres gas produced, bubble gas through limewater
sulfate test
BaSO4 is insoluble
aqueous barium ions added to solution of unknown compound
sequence of tests
carbonate
sulfate
halide
test for ammonium ion
add NaOH (aq) to solution of ammonium ion
ammonia gas produced
mixture warmed, gas released
test with moist pH indicator paper
paper turns blue is ammonia is present
