Group 7/ The halogens Flashcards
what are the properties of group 7 atoms
very reactive non metals
gain one electron when ionised
exist as diatomic molecules
non polar
what is the trend in electronegativity in group 7 as u go down the group
Electronegativity decreases
Because : number of energy levels increases
so weaker attraction between nucleus and electrons in a covalent bond
what is the trend in boiling point ad u go down group 7
increased
because side of atom increases so more electrons
more london forces between the molecules that need to be broken
What is the appearance of fluorine at room temp
pale yellow
gas
appearance of chlorine at room temps
pale green
gas
appearance of bromine at room temp
dark red/orange
liquid
appearcje of iodide at room temp
dark blue/black
solid
What is an oxidising agent
electron acceptor
gained electrons
is reduced
trend in ability of halogens to act as oxidising agents down group 7
decreased
they become less reactive down the group
why do halogens become less reactive down the group
atomic readings increases
shielding increases
halogen atom gains an electron less easily
because there’s a weaker attraction from the nucleus
how can halide ions be identified in solution
used acidified silver nitrate
ionic equation for adding acidified silver nitrate to a halide
Ag+ (aq) + X- (aq) -> AgX
What observation is made when F- is reacted with silver nitrate
No visible chnage (as AgF is soluble)
AgF (aq)
Observation made when chloride ion reacts with silver nitate
silver halide : AgCl (s)
White ppt
Observation when Bromide ions and reacted with silver nitste
silver halide : AgBr (s)
Cream ppt
Observation between Iodide ion and silver mirage
silver halide : AgI (s)
yellow ppt
what happens if carbonate and hydroxide ions are not removed
they will form a ppt with silver ions so they have to be removed otherwise they interfere with the test
we acidify the solution with nitric acid to remove these ions
why can’t we use HCL to acidify the solution
HCL contains Cl- ions and would form a white ppt of silver chloride (AgCl(s))
what is the trend in solubility of silver halide in ammonia down group 7
solubility decreases
reaction of chlorine with water
Cl2(g) + H2O(l) —\ HCl(aq) + HClO(aq)
\—
equilibrium
what is disproportionation
oxidation and reduction of the same element
how should we use chlorine
is very small amounts because it’s toxic
reaction between chlorine and NaOH
Cl2 + 2NaOH -> H2O + NaCl + NaClO
how do you test for carbonate ions
carbonate ions release CO2 and water when reacted with an acid
add dilute nitric acid and test the gas protected with limewater
result for test dir carbonate ions
effervescence
and gas produced (CO2) will turn the lime water cloudy
test for sulfate ions
make a solution of the compound
add some acidified barium nitrate solution
result for test for sukfate ions
white ppt of BaSO4
test for chlorine ions with acidified silver notate
white ppt
