8.2 The Halogens Flashcards
How do the halogens occur on Earth
As stable halide ions Cl- Br- and I-, dissolved in sea water or combined with sodium or potassium as solid deposits such as in salt mines
At RTP, all halogens exist in ______ molecules
Diatomic
In their solid states, the halogens form ______ with ______ molecular structures
Lattices
Simple
How many electrons are in the outer shell of a halogen
7
What type of reaction is the most common for the halogens
Redox
Halogen is reduced gaining one electron
What do the results of a displacement reaction of halogens with halide ions show
That the reactivity of the halogens decreases down the group
If the halogen added is more reactive than the halide present:
A reaction takes place, the halogen displacing the halide from solution
The solution changes colour
How can you tell the difference between iodine and bromine
An organic non-polar solvent such as cyclohexane can be added and the mixture shaken
The non-polar halogens dissolve more readily in cyclohexane than in water
The colours are much easier to tell apart with iodine being a deep violet
Fluorine gas
Pale yellow gas
Reacts with almost any substance it comes in contact with
Why is Astatine extremely rare
It is radioactive and decays rapidly and the element has never been seen
How do halogens react in redox reactions
Gain electrons
Trend in reactivity of halogens
The tendency to gain an electron decreases and they become less reactive going down the group
Atomic radius increases, more inner shells so shielding increases, less nuclear attraction to capture an electron from another species
Which of the halogens is the strongest oxidising agent
Fluorine
Gains electrons from other species more readily than the other halogens.
What is disproportionation
A redox reaction in which the same element is oxidised and reduced
What name is given to a reaction where the same element is both oxidised and reduced
A disproportionation reaction
