3.1 Elements from the Sea

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3.1 Elements from the Sea
Group 7 Halogens
Have 7 electrons in their outer shell
Most reactive group of non-metals
Occur naturally as diatomic molecules e.g. Br2, Cl2, As2
They achieve stability by:
Forming a halide ion and gaining an electron from a metal in an ionic bond
Sharing an electron covalently with another non-metal
Trend Colour (in Melting/Boilin Volatility Reactivity State at 298K Electronegativity
: solution) g Point 101kpa
Cl2 Pale green Low Volatile V. Reactive Gas V. Electronegative
Br2 Orange Liquid
I2 Brown (violet high Less Volatile Less Reactive Metallic grey Solid Not V.
in cyclohexane) Electronegative
Chlorine is more reactive than Iodine as it is a smaller molecule. All group 7 elements usually have
a +7 charge. Because Chlorine is smaller than Iodine, it has a higher charge density as there is a
higher ratio of charge to the size of the ion.

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Halogens push less reactive halogens from a compound. This is called a displacement reaction:
This reaction is also a redox reaction as both oxidation and reduction take place.
Halogens replace less reactive halides.
Halogens in cyclohexane Halides reacting with silver to form precipitates
Halide ions react with silver ions to form precipitates.…read more


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