Topic 8- Group 7 Elements Flashcards
What are atoms of group 7 called?
What are ions of group 7 called?
What type of molecules do halogens form?
What happens to the size of the atoms in group 7?
What does each element have going down the group?
What are the three factors affecting the attraction between the nucleus and the bonding electrons?
What happens to melting and boiling points as you go down the group?
What do larger atoms have and therefore what does this make stronger?
What are the colours of the following halogens and in what states:
Fluorine
Chlorine
Bromine
Iodine
Halogen
Halides
Diatomic molecules
The atoms get bigger as we go down the group
Each has an extra filled main level of electrons
- The nuclear charge
- Distance to the bonding (outer) electrons
- Shielding effect of the inner shell electrons
These increase as you go down the group
Larger atoms have more electrons and this makes the van der Waals forces between the molecules stronger
Pale yellow gas
Greenish gas
Red-brown liquid / orange fumes
Black solid / purple vapour.
What does 1 cm3 equal in ml?
What type of agents are halogens?
What do halogens need to complete their octet?
What happens to the oxidising power down group 7?
How can this trend be explained?
What two things is this offset by?
What happens to the oxidising ability you go up the group?
What is the electronic configuration of all the halogens?
What is used to demonstrate the decrease in reactivity down the group?
How is this done?
1 cm3 = 0.5 ml
Halogens are oxidising agents
They need one electron to complete their octet
The oxidising power gets weaker down the group
Increasing the nuclear charge which should attract electrons more
- Increasing shielding
- Increasing atomic radius
The oxidising ability of halogens increases as you go up the group
ns2 np5
Displacement reactions
A solution of the halogen is added to a solution of a halide.
What are halides?
What will a more reactive halogen do?
What is the equation for the reaction of chlorine with water?
What is the equation for the reaction of chlorine with water in sunlight?
What can chlorine do to water in sunlight?
What is a redox reaction?
What is the definition of a disproportionation reaction?
What is the equation for the reaction of chlorine with sodium hydroxide?
What is a use of chloric (I) acid and what does it do?
What are two benefits of water treatment with chlorine?
What are two risks of water treatment with chlorine?
What is the overall outcome of water treatment with chlorine?
Halides are salts formed from halogens
A more reactive halogen will displace a less reactive one
Cl2 (g) + H2O (l) <===> HClO (aq) + HCl (aq)
Cl2 (g) + H2O (l) <===> 2H+ (aq) + 2 Cl- (aq) + 1/2 O2 (g)
In sunlight, chlorine can decompose water
Reduction and oxidation
When a species is simultaneously reduced and oxidised so as to form two different products
Cl2 (g) + 2NaOH (aq) <===> NaClO (aq) + NaCl (aq) + H2O (l)
It’s a bleach and kills bacteria
+ Chlorate (I) ion kills bacteria
+Prevents growth of algae, bad tastes and smells and discolouration from organic compounds
- Harmful gas
- Many chlorinated hydrocarbons are carcinogenic
The benefits outweigh the risks.
What does it mean the more positive the oxidation state?
What does it mean the more negative the oxidation state
What happens to atomic radius in the halogens?
What happens to ionic radius in the halogens?
What two things happen the greater the atomic number?
What are ions compared to atoms?
The more positive, the more oxidised
The more negative, the more reduced
Atomic radius increases down group
Ionic radius increases down group
The more electrons there are, that go into shells increasingly further from the nucleus
Ions are larger than atoms.
What happens to the radius of ions and why?
Why do the atoms get bigger as you go down the halogens?
What happens to electronegativity in group 7?
What should the increasing nuclear charge do and why?
What happens as a result of an increasing number of shells?
What happens as a result of an increasing atomic radius?
The added electrons repels the others so radius gets larger
Because each halogen has an extra filled main shell of electrons compared with the one above it
Decreases down the group
The increasing nuclear charge due to the greater number of protons should attract electrons more
There is therefore more shielding and less pull on electrons
Therefore attraction drops off as distance increases.
What do all metal halides do and what does this form?
What is an example equation of this (symbol)?
What is the one exception?
What precipitate is formed for the following halides added with silver nitrate solution:
F-
Cl-
Br-
I-
What colour is produced for the following halides in aqueous solution added with silver ions:
Silver Fluoride
Silver Chloride
Silver Bromide
Silver Iodide
What happens to the following halides in further tests:
Silver Fluoride
Silver Chloride
Silver Bromide
Silver Iodide
All metal halides react with silver ions (aq) to form a precipitate
Cl- (aq) + Ag+ (aq) —> AgCl (s)
F- (fluoride ions)
No precipitate
White precipitate
(very pale) Cream precipitate
(very pale) Yellow precipitate
No precipitate
White precipitate
Cream precipitate
Yellow precipitate
No precipitate
Dissolves in dilute ammonia
Dissolves in concentrated ammonia
No precipitate.
What is the equation for the test for sulphate ions (symbol)?
What precipitate does this reaction form?
Why do the bond energies decrease going down group 7- from Cl2 to I2 (full description)?
Why does F2 have an unexpectedly low bond energy (full description)?
What does this mean happens to the fluorine (full description)?
MgSO4 + BaCl2 —> MgCl2 + BaSO4 (s)
A white precipitate
A covalent bond works because the bonding pair is attracted to both the nuclei at either side of it. It is that attraction which holds the molecule together. The size of the attraction will depend, amongst other things, on the distance from the bonding pair to the two nuclei
Because the small size of the fluorine atom leads to repulsion between non-bonding electrons because they are so close together
This means the fluorine bond is broken relatively easily and so fluorine is extremely reactive.
