2.3 - Group 7: The Halogens Flashcards
Uses of bromine?
- flame retardants
- fire extinguishers
What are the uses of chlorine?
Water purification + bleaching
uses of iodine?
- antiseptic
- disinfecting agents
What happens to the colours as you go down the group?
They get darker.
State the colours of the following:
- Flourine
- Chlorine
- Bromine
- Iodine
- Flourine -> pale yellow gas
- Chlorine -> green/yellow gas
- Bromine -> orange/brown liquid
- Iodine -> Grey/black solid, purple vapour
What happens to the BP and MP as you go down the group?
refer to volatility
- They increase down the group which indicates that the elements become less volatile.
- Florine is the most volatile while iodine is the least.
What is volatility?
How easily a substance can evaporate.
What type of bonds are formed in halogens?
- They are diatomic molecules so they form covalent bonds.
What happens to the bond strength as you go down the group?
- It gets weaker as atomic size increases
- The bonding pair of electrons get further away from the halogen nucleus and are therefore less strongly attracted towards it
What happens to the bond enthalpies and what does it indicate?
- The bond enthalpies decrease as you go down the group which means that bond strengths also decrease.
What is bond enthalpy?
- The energy needed to break one mole of covalent bonds.
- Higher the enthalpy, the stonger the bond
Describe the Van der Waals forces in halogens.
- Larger the molecule, the stronger the van der waals forces.
- This is why it gets harder to seperate bonds as you go down the group which means that mp and bp increase.
- Because it gets more difficult to seperate molecules, the volatility of the halogens decreases going down the group.
- Going down the group, the van der Waals’ forces increase due to an increased number of electrons in the molecules which means that the volatility decreases.
How are halogens oxidising agents?
- Halogens oxidies metals by removing an electron from the metal to become a 1- ion (the oxidation number of the metal increases).
- Halogens become reduced as they gain an extra electron from the metal atom (the oxidation number of the halogen decreases).
What happens to the electronegativity as you go down the group?
It decreases due to an increase in atomic radius so therefore an increase in shielding.
What are halide ions?
- They can act as oxidising agents and donate electrons to another atom
- They themselves can be oxidised and lose electrons
- Reducing power of the halide ions increases going down the group
- Halide ions become larger
- The halide ions lose electrons more easily due to the outermost electrons being held less tightly and so their reducing power increases.
