8.2 Group 7 Flashcards
what are the physical properties of group 7 elements?
most reactive non-metal group
do not occur in their natural state
what is the trend in boiling point in group 7?
the boiling point increases as you go down the group
why does the boiling point increase as you go down group 7?
increased number of electrons
stronger London forces
more energy is needed to overcome the stronger forces
appearance and state of F2
pale yellow
GAS
appearance and state of Cl2
pale green
GAS
appearance and state of Br2
red-brown
LIQUID
appearance and state of I2
shiny grey
SOLID
what is the electronic configuration of group 7 elements?
7 electrons in outer shell
2 electrons in s sub-shell
5 electrons in p sub-shell
why are group 7 elements oxidising agents?
they gain an electron to form -1 ions
Cl2 + e- ——–> 2Cl-
they accept electrons given from another species which means it has had to oxidise another species
what is the trend in reactivity of group 7 elements?
reactivity decreases because as you go down the group:
- atomic radius increases
- shielding increases
- less nuclear attraction between nucleus and electrons
- less ability to attract an electron to ionise
what is a disproportionation reaction?
when oxidation and reduction happens in the same reaction to the same species
what is an example of a disproportionation reaction?
chlorine and water
chlorine and sodium hydroxide
chlorine + water
chloric (I) acid
hydrochloric acid
chlorine + water equation
Cl2 (aq) + H2O (l) ——-> HClO (aq) + HCl )aq)
Cl in Cl2
= 0
Cl in HClO
= +1 (oxidation)
Cl in HCl
= -1 (reduction)
chlorine has been oxidised and reduced so this is a disproportionation reaction
what is HClO?
chloric (I) acid
it is what kills bacteria in bleach
acts as a weak bleach
