The halogens Flashcards
in which block are the halogens
p-block
state and colour of fluorine
pale yellow gas
state and colour of chlorine
green gas
state and colour of bromine
red-brown liquid
state and colour of iodine
black solid
what factors increase down group 7
- nuclear charge
- number of e-
- atomic radius
- boiling point
why does the boiling point of the halogens increase down the group
- more electrons moving down the group, strength of the temporary dipoles increases.
- Increased dipoles mean greater London forces
what type of reactions are halogens often involved in
- redox reactions
- they gain 1 e- to form 1- halide ion
why does electronegativity decrease down group 7
- increase in atomic radii
- shielding outweighs the increase in nuclear charge
- less attraction between nucleus and valent e-
why is fluorine the most reactive
- atomic radius increases down the group
- greater shielding
- less nuclear attraction to attract an electron from another species
what happens when a more reactive and less reactive halogen react
- more reactive halogen will displace a less reactive halide ion from solution resulting in a colour change corresponding to the displaced halogen
why are halogens less reactive down group 7
- decreasing electronegativity reduces halogen’s ability to attract and e- to form 1- ion
what can be done to make colour change in displacement reactions easier to see
- in a separating funnel, shake the reaction mixture with an organic solvent like hexane
- non-polar halogen dissolves in non-polar organic solvent
- polar halide dissolves in aq layer
- organic layer above aq
what colour is chlorine in water
pale green
what colour is bromine in water
orange
what colour is iodine in water
brown
in non-polar organic solvent chlorine is
pale yellow-green
in non-polar organic solvent iodine is
purple
in non-polar organic solvent bromine is
yellow-orange
ionic equations for displacement reactions
X2 (aq) + 2Y- (aq) –> Y2(aq) + 2X- (aq)
- the more reactive species ends up as ions
are halogens oxidising or reducing agents
they’re oxidising agents and become reduced themselves
define disproportionation
when a single element is simultaneously oxidised and reduced in a reaction
equation for the disproportionation of chlorine when reacted with water
Cl2(aq) + H2O(l) —> HCl (aq) + HClO(aq)
- Cl reduced from 0 in Cl2 to -1 in HCl
- Cl oxidised from 0 in Cl2 to +1 in HClO
why is chlorine used in water purification
on addition to water, the products, chloric (I) acid, HClO, and the Cl- ion, effectively kill bac
