3.1.3 Groups 17: The Halogens Flashcards
What are the main two properties of halogens?
> low melting and boiling points
> they exist as diatomic molecules, x^2 where x represents the halogen
What is the trend in boiling points of halogens?
> Moving down the groups, the boiling point increases
Number of electrons increase
Which increases the strength of London forces
More energy required to break the intermolecular forces
Describe the reactivity of the halogens
Halogens are very reactive and highly electronegative
Describe halogens as oxidising agens
They are very good at attracting and capturing electrons which means the are strong oxidising agents
What happens to halogens during reactions
Each atom gains an electron to form 1- ions known as halide ions
What is the trend of the reactivity and oxidising power of halogens?
It decreases as you move down the group, this is because:
> Atomic radius increases
> Electron shielding increases
> The ability to gain an electron in the p sub-shell to form an 1- ions decreases
Definition of displacement reaction
A more reactive halogen will oxidise and displace a halide of a less reactive halogen
Cl2 colour in water & colour in cyclohexane
Pale Green in both
Br2 colour in water & colour in cyclohexane
Orange in both
l2 colour in water & colour in cyclohexane
brown in water and violet in cyclohexane
Show the oxidation of chlorine:
Cl2 (AQ) + 2BR- (AQ) –>
Cl2 (AQ) + 2BR- (AQ) –> 2Cl-(AQ) + Br2 (AQ)
Show the oxidation of chlorine:
Cl2 (AQ) + 2I- (AQ) –>
Cl2 (AQ) + 2I- (AQ) –> 2Cl-(AQ) + I2 (AQ)
Show the oxidation of Bromine:
Br2 (AQ) + 2I-(AQ) –>
Br2 (AQ) + 2I-(AQ) –> 2Br- (AQ) + I2(AQ)
Definition of Disproportionation
Its the oxidation and reduction of the same element in a redox reaction
Uses & risks of reacting Cl2 + H2O
> Cl2 kills bacteria, making water safer to drink (purification of water)
Hazard of toxic chlorine gas
