group 7 - paper 1 Flashcards
what happens to the electronegativity of group 7 going down the group
-Electronegativity decreases down group 7
-This is because electron shielding increases down the group
-It is harder for the atom to attract a pair of electrons in a covalent bond because there is weaker attraction between nucleus and outer electron shell
State and explain the trend in electronegativity down group 7
- atoms become less electronegative
- electron shielding increases
- distance between nucleus and outer electron shell increases
- it is harder for nucleus to attract a pair of electrons in a bond
Describe the structure and bonding of the halogens
- diatomic molecules (e.g. Cl2)
- covalent bond (shared pair of electrons) between 2 halogen atoms
- weak VdW forces between molecules
State and explain the trend in boiling points of the halogens
- boiling points increase down group 7
- molecules become larger/larger surface with more electrons
- strength of VdW forces increase
- require more energy to overcome
How does the appearance of the halogens change going down the group?
they become darker and denser
Why are many of the properties fluorine considered untypical?
-The F-F bond is weaker than expected
-This is because the F atoms are smaller and there is repulsion between non-bonding electrons
How does the oxidising ability of the halogens change going down the group?
It will decrease going down the group
What happens in a displacement reaction?
-Halogens react with metal halides in a solution in such a way that the halide in the compound will be displaced by a more reactive halogen
How does the reducing power of the halogens change going down the group?
-The halides become more reducing as you go down the group.
-The larger the ion, the more easily it can give away an electron
What is the simplest ionic equation for the reaction of solid NaCl with concentrated sulfuric acid? What is an observation of this reaction?
Cl- + H2SO4 –> HCl + HSO4-
Steamy,white fumes, turns litmus paper red
What is the simplest ionic equation for the reaction of solid NaBr with concentrated sulfuric acid? What is an observation of this reaction?
2Br- + H2SO4 + 2H+ –> Br2 + SO2 + 2H2O
Orange vapour and choking gas
What are the ionic equations for the reaction of solid NaI with concentrated sulfuric acid? What are the observations of these reactions?
6I- + H2SO4 + 8H+ –> 3I2 + S + 4H2O
yellow solid produced and purple vapour
8I- + H2SO4 + 8H+ –> 4I2 + H2S + 4H2O
foul smelling gas and purple vapour
he reaction of Cl and water is an example of what type of reaction?
disproportionation
What is a disproportionation reaction
A reaction where an element is being both reduced and oxidised.
When using ammonia to test for Cl- ions, what is the expected result?
The ppt. will dissolve in dilute ammonia
