Group 7
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What colour is chlorine at RTP?
Green
What colour is bromine at RTP?
Brown
What colour is iodine at RTP?
Grey
What state is chlorine at RTP?
Gas
What state is bromine at RTP?
Liquid
What state is iodine at RTP?
Solid
What is the trend in boiling points down the group?
Boiling points increase down the group
Why do boiling points increase down the group? (extended answer)
• further down the group halogen MOLECULES contain more electrons • the electron cloud can become more unevenly distributed • larger dipoles can be induced in neighbouring molecules • attraction between larger dipoles means stronger London forces • stronger London forces require more energy to be overcome
Why do boiling points increase down the group? (short answer)
• more electrons • stronger London forces • more energy required to break the intermolecular forces • boiling point increases
Why are Cl-Cl bonds the strongest?
• the covalent bonds are formed by a shared pair of electrons being attracted to the nuclei of the bonded atoms • the closer electrons are to the nucleus the stronger the attraction • chlorine is the smallest atom • smaller atoms have a higher nuclear charge
Why are halide ions larger than their atoms?
• an additional electron has been added • this leads to greater repulsion between the electrons • meaning ions are smaller
What can be added to a halide solution to test for which halide ion is present?
An organic solvent, such as cyclohexane or hexane
When cyclohexane is added to a solution containing chloride ions, what would be seen?
Two layers form, the top one pale green
When cyclohexane is added to a solution containing bromide ions, what would be seen?
Two layers form, the top one orange
When cyclohexane is added to a solution containing iodide ions, what would be seen?
Two layers form, the top one violet
When the mixture of halide solution and hexane is shaken why does the colour of the top layer become more vivid?
• halogens are much more soluble in the organic layer • shaking assists the movement of the halogens into the organic layer • as their concentration increases, the colour becomes more vivid
What is the colour of Cl2 in water?
Pale green
What is the colour of l2 in water?
Brown
What is the colour of Br2 in water?
Orange
Which halogen is the most powerful oxidising agent?
Fluorine
Which halogen is the least powerful oxidising agent?
Astatine
What is the trend in reactivity down the group?
Reactivity decreases
Why does reactivity decrease down the group?
• halogens react by gaining an electron • no. shells increases down the group • shielding increases • atomic radius increases • attraction of the nucleus to electrons decreases
Does chlorine react with Br-, I-, or both?
Both