Group 7 ( The halogens) Flashcards
State the main properties of the Halogens
Fluorine - Pale yellow - Gas
Chlorine - Green - Gas
Bromine - Red-brown - liquid
Iodine - Grey - solid
State the colour of the halogens in water
Chlorine - virtually colourless
Bromine - yellow/orange
Iodine - Brown
State the colour of the halogens in hexane
Chlorine - Virtually colourless
Bromine - Orange/red
Iodine - Pink/violet
What is the trend in first ionisation energy of the halogens
The first ionisation energy decreases down the group, because the electrons are held further away from the nucleus, meaning a weaker attraction , therefore less energy required to remove an defections
Explain the trends melting and boiling points of the halogens
-As you go down the group the melting and boiling points increase
-This is because as you go down there is an increase in electron shells, which mean there are more electrons.
-Therefore this means the London forces between the halogen molecules get stronger
-This increase in London forces makes it harder to overcome the intermolecular forces, so therefore more energy is require to break these forces
Explain the trend in reactivity of the halogens going down the group
-As you go down the group the reactivity decreases
-This is because the atoms become large going down the group, so their outer electrons are further away from the nucleus. Therefore there is a greater shielding effect.
-Therefore there is a weaker attraction between the nucleus and the outer shell electrons. Making it harder for larger atoms to attract the electron needed to form an ion
Explain the trend in electronegativity of the halogens going down the group
-The electronegativity decreases going down the group
-There are more energy levels as you go down the group
-Therefore the distance between the nucleus and bonding pair of electrons is bigger
-So there is a weaker attraction between them, so therefore harder to attract an electron
Explain the reactions between the halogens and the metal in Group 1 and 2
This reaction involves an electron transfer to the halogen, -The reaction is a redox reactions in which the halogen reacts as an oxidant agent
-The halogen is reduced as it gains an electron
-The oxidation number of the halogens decrease from 0 to -1, shears the oxidation number of the metal increase from 0 to +1 or +2
-The product is usually ionic solids which are white
Sample Equations:
* Lithium reacting with chlorine 2Li + Cl2 → 2LiCl
* Barium reacting with chlorine 2Ba + Br2 → 2BaBr
What is a displacement reaction
It is a type of reaction where one element(more reactive) replaces another element(less reactive) in a compound
-Chlorine displaces bromine and iodine
-Bromine displaces iodine but not chlorine
-iodine does not displace either chlorine or bromine
Write an equation which a halogen displace the halide ions from the solution
Cl2(aq) + 2KBr(aq) → 2KCL(aq) + Br2(aq)
Chlorine added to potassium bromide - Chlorine displaces bromine
Cl2 + 2Br- → 2Cl- + Br2
The ionic equation
These reactions occur in aqueous solution
These equations are example of redox reactions. The reacting halogen is reduced, the reacting halide is oxidised. Chlorine displaces bromine and is reduced, bromine is displaced by chlorine and gets oxidised.
There will be a colour change from colourless to orange
Explain why chlorine is the most reactive out of the three
-It has the smallest atom, so the incoming electron gets closer to and is more attracted to the nucleus
-It has the smallest number of inner energy levels of electrons, so the incoming electron experiences the least repulsions
Explain the reaction between chlorine and water and what it’s used for
This reaction is a disproportionation reaction
Cl2(g) + H2O(l) → HCL(aq) + HCIO(aq)
Forms hydrochloric acid and hypochlorous acid
Chlorine is reduced and is oxidised
HCIO(aq) + H2O(l) → ClO-(aq) + H3O+(aq)
Hypochlorous acid ionises to make chlorate ions (also called hypochlorite)
Adding chlorine is used to kill bacteria, and can make it safe to drink or swim in water
Show the reaction of chlorine with cold alkalis
When chlorine is added to cold dilute sodium hydroxide, it reacts to from the salts of the acid. These salts are sodium chloride and sodium chlorate
Cl2(g) + 2NaOH(aq) → NaClO(aq) + NaCl(aq) + H2O(l)
This reactions forms bleach, because sodium chlorate(I) solution just happens to be bleach. Which is used as a disinfectant
Show the reaction of chlorine and hot alkalis
When chlorine is added to hot concentrated sodium hydroxide solution, it reacts to form sodium chloride and sodium chlorate(v) which are different products
3Cl2(g) + 6NaOH(aq) → 5NaCl(aq) + NaCLO3(aq) + 3H2O(l)
The sodium chlorate formed is also used in bleaching, and as a weed killer
What is meant by having a strong reducing agent
It is when the substance has a strong tendency to lose electrons, since it will reduce the other substances by donating electrons. Atoms with relatively large atomic radii tend to be better reductants.
Bromide and Iodide are the best reducing agents. Whereas Chlorine is not strong enough reducing agent to reduce sulfuric acid
