Chemistry: Group 7 Part 1
This flashcard set explores the properties of Group 7 elements, known as the halogens. It covers their electron configuration, structural form as diatomic molecules, and explains the increasing atomic radius trend down the group due to additional electron shells being added.
what are group 7 elements known as
the halogens
Key Terms
what are group 7 elements known as
the halogens
how many outer electrons do group 7 elements have
7
why are group 7 elements in the p block
their outer electrons are in the p subshell
what do group 7 elements exist as
diatomic molecules
what is the trend in atomic radius down the group
increases
why does atomic radius increase down the group
more shells-more shielding
nuclear attraction on outer electrons decreases
atomic radius increases
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| Term | Definition |
|---|---|
what are group 7 elements known as | the halogens |
how many outer electrons do group 7 elements have | 7 |
why are group 7 elements in the p block | their outer electrons are in the p subshell |
what do group 7 elements exist as | diatomic molecules |
what is the trend in atomic radius down the group | increases |
why does atomic radius increase down the group |
|
why is the ionic radius of a group 7 element bigger than the atomic radius |
|
trend in boiling point down group 7 | increases |
what is the trend in volatility down the group | they become less volatile |
why does boiling point increase (and volatility decrease) down group 7 | -Mr increases- more electrons |
trend in electronegativity down group | decreases |
why does electronegativity decrease down group |
- nuc attraction on outer electron decreases as atomic radius increases |
trend in first ionisation energy down group | decreases |
why does first ionisation energy decrease |
- nuc attraction on outer electron decreases as atomic radius increases |
appearance of chlorine | pale green gas |
state of chlorine at room temperature | gas |
colour of aqueous solution of chlorine | very pale green |
colour of chlorine in cyclohexane | very pale green |
appearance of bromine | red/brown liquid |
| liquid |
colour of bromine in aqueous solution | orange |
colour of bromine in cyclohexane | orange |
appearance of iodine | grey solid |
| solid |
colour of iodine in aqueous solution | brown |
colour of iodine in cyclohexane | purple |
why are halogens more soluble in cyclohexane than water | they themselves are non polar like cyclohexane |
trend in solubility of halogen in water down group | decreases |
why does solubility in water decrease down group | halogen molecule becomes larger |
what does a series of displacement reactions provide evidence for | the trend in oxidising powers of the halogens |
method for displacement reactions |
|
what will the colour of the organic layer in displacement reactions tell you | which halogen is now present |
colour of organic top layer: | KBr + Cl2 | orange- Br2 |
colour of organic top layer: | KI + Cl2 | pink/purple - I2 |
colour of organic top layer: | KCl + Br2 | orange- Br2 |
colour of organic top layer: | Br2 + KI | purple/pink- I2 |
colour of organic top layer: | I2 + KCl | purple/pink- I2 |
colour of organic top layer: | KBr + I2 | pink/purple- I2 |
oxidising agent | substance which accepts electrons |
why are halogens oxidising agents | they all take electrons readily to form ions X2 +2e- > 2X- |
what happens to the halogens ability to act as oxidising agents as you go down the group | decreases |
why does halogens ability to act as oxidising agents decrease down group |
|
trend in reactivity Cl2 > Br2 > I2 | chlorine most reactive- iodine least |
if X is higher up in group than Y… | X is able to oxidise Y |
what is a reducing agent | electron donor (is itself oxidised) |
can halide ions act as reducing agents | yes but to different extents |
what is the oxidation number of sulphur in sulphuric acid | +6 |
test for sulphuric acid | indicator paper turns red |
oxidation number of sulphur in sulphur dioxide | +4 |
test for sulphur dioxide | acidified dichromate paper: orange > green |