Group 7 Flashcards
What group are the halogens in? Why?
Group 7 because they have 7 outer shell
electrons.
What is the colour and state of chlorine at room
temperature?
Pale green gas
What is the colour and state of bromine at room
temperature?
Red-brown liquid
What is the colour and state of iodine at room
temperature?
Black solid
Why are the halogens at different states at room
temperature? What is the trend down the group?
At room temperature, chlorine is gaseous,
bromine is liquid and iodine is solid because they
have different melting and boiling points. As you
go down the group, melting and boiling point
increases.
What state would you expect the halogens fluorine
and astatine to be at room temperature?
Fluorine is above chlorine so should have a boiling point
lower than chlorine. This means it would be a gas at room
temperature.
Astatine is below iodine in group 7 so should have a higher
melting point than iodine. Therefore you can predict that it
would be a solid at room temperature.
Why does melting and boiling point increase down Group 7?
The molecules get bigger down the group so there are more intermolecular forces to overcome during melting / boiling so more energy is required.
What is the chemical test for chlorine?
Damp litmus paper placed into a test
tube of gas. If chlorine is present, the
litmus paper will turn red then white due
to the bleaching effect of chlorine
Halogens are diatomic. What does this mean?
They form molecules consisting of 2
atoms
E.g: Cl2 , Br2…
What charge does a halide ion carry? Why?
- 1
e. g. Cl-, Br-…
They gain one electron to have a stable
electron configuration.
What is produced when a halogen reacts with a
metal?
Metal halide salt
Write a balanced symbol equation for the reaction
between bromine and sodium
Br2 + 2Na → 2NaBr (check google if unsure)
Write a balanced symbol equation for the reaction
between chlorine and calcium
Cl2 + Ca → CaCl2 (check google if unsure)
Predict the product of the reaction between
magnesium and fluorine
Magnesium fluoride (MgF2)
Write a word equation for the reaction between
iodine and potassium
Iodine + potassium → Potassium iodide.
Remember: the ion of a halogen ends
with -ide.
Describe the trend in reactivity of the halogens. How
does this affect the rate of reaction?
Reactivity decreases down group 7.
Rate of reaction decreases down group 7
What is formed when hydrogen reacts with a
halogen?
Hydrogen halides
e.g. HCl, HBr…
Chlorine reacts with hydrogen in the presence of
sunlight but bromine requires a flame. Why?
Reactivity decreases down the group so
bromine requires more energy for the
reaction to occur
What is formed when a hydrogen halide dissolves in
water?
An acidic solution. Hydrogen ions
dissociate, making the solution acidic.
Write a balanced symbol equation for the reaction
between hydrogen and chlorine
H2 + Cl2 → 2HCl (check if unsure)
Predict the product of the reaction between
hydrogen and fluorine
Hydrogen fluoride (HF)
When does a halogen displacement reaction occur?
When a more reactive halogen displaces
a less reactive halogen from an aqueous
solution of its halide.
Why will halide ions A only be displaced by halogen
B if B is above A in group 7?
The most reactive halogen (B) will displace the
less reactive halogen (A) to become part of the
ionic compound. Reactivity increases as you go
up the group so B must be higher in group 7 to
be more reactive than A
Which halogens can chlorine displace from an
aqueous ionic solution?
Chlorine can displace any halogens
below it in group 7. It will displace iodine
and bromine.
Which halogens can’t be displaced from an aqueous
ionic solution by bromine?
Bromine can’t displace any halogens
above it in group 7. These are chlorine
and fluorine.
Why can iodine not displace chlorine or bromine
from an aqueous ionic solution?
Because reactivity decreases down the group
and iodine is below chlorine and bromine
group 7. Displacement will only occur if iodine
is more reactive than the halogen in the ionic
compound.
Write the word equation for the reaction between
chlorine and potassium bromide
Chlorine + potassium bromide → potassium chloride + bromine
Write the word equation for the reaction between
bromine and calcium chloride
No reaction will occur because bromine
is less reactive than chlorine so chlorine
won’t be displaced.
Write the balanced symbol equation for the reaction
that takes place between bromine and potassium
iodide
Br2 + 2KI → I2 + 2KBr (check google if unsure)
Which halogens would you expect astatine to be
able to displace?
None of them. It is at the bottom of group
7 so has the lowest reactivity.
Why does reactivity decrease down group 7?
As you go down group 7, the outer shell is further
from the nucleus and electron shielding increases.
Attraction between the nucleus and outer electrons
decreases so it is harder for the atom to gain an
electron meaning reactivity decreases.
What colours are solutions of chlorine, bromine and
iodine?
Chlorine water - colourless
Bromine water - orange
Iodine solution - brown
What would you observe when chlorine is added to
potassium bromide?
Cl2 + 2KBr → Br2 + 2KCl
Colour change from colourless (due to Cl2) to orange (due to Br2).
What is a redox reaction?
A reaction where oxidation and reduction
take place at the same time.
Are halogen displacement reactions redox
reactions? Explain your answer
Yes because the halide ion is oxidised (loses an
electron) to form a halogen atom and the halogen
is reduced (gains an electron) to form a halide
ion.
Write the two half equations for the reaction between
chlorine and potassium bromide, stating which is
reduction and which is oxidation
Overall equation: Cl2 + 2KBr → Br2 + 2KCl
Reduction: Cl + 2e- → 2Cl2
Oxidation: 2Br- → Br + 2e
Bromine reacts with potassium iodide. What is
reduced and what is oxidised?
Bromine is reduced to bromide ions.
Iodide ions are oxidised to iodine.
