3.2.3.1 Trends in properties (group 7) Flashcards
What is the formula and name for all halide ions?
1-, -ide
What is the state and appearance of fluorine at room temperature and its characteristics?
Very pale yellow gas
Highly reactive
What is the state and appearance of chlorine at room temperature and its characteristics?
Greenish and reactive gas
Poisonous at high concentrations
What is the colour of fluorine in a solution?
No colour, doesn’t really form solutions
What is the colour of chlorine in solutions?
Often colourless, other times very pale green
What is the state and appearance of bromine at room temperature and its characteristics?
Red liquid
Gives off dense brown poisonous fumes
What is the colour of bromine in solutions?
Yellow solutions
What is the state and appearance of iodine at room temperature and its characteristics?
Shiny grey/black solid, sublimes to purple gas
Solid sublimes to purple gas
What is the colour of iodine in solutions?
Brown solution (sometimes black solid present)
Describe the trend of electronegativity down group 7
Decreases, number of shells increases down the group, shielding effect increases, attraction between nucleus and shared electron pair decreaes
Describe the trend of boiling points down group 7
Increases from F to I, molecules have more electrons, Van der Waal’s forces become stronger, so more energy needed to overcome forces
What are the chemical properties of halogens?
Gain electrons in chemical reactions
Reactivity of halogens decreases down group 7
They are good oxidising agents
What is the trend in oxidising abilities of halogens?
F2>CL2>Br2>I2
Describe the trends in reducing ability of the halide ions
Going down the group, reducing ability increases
because halide ion becomes larger as they have more electron shells. Halide ions have greater shielding effect, so it is easier to lose outer electrons as they are less strongly held by nucleus.
Describe the reaction of NaF with conc. H2SO4
Acid-base step: NaF(s) +H2SO4 (l) -> NaHSO4(s) +HF(g)
F- ions are not strong enough reducing agents to reduce the S in H2SO4, so no redox reaction occurs
Observation: White steamy fumes