Inorganic - 2.3 Group 7 Flashcards
Define displacement
Chemical reaction in which one element replaces another element in a compound. A halogen would displace a halide from solution if the halide is below it in the periodic table.
What is a disproportionation reaction?
A reaction in which substance is simultaneously reduced and oxidised. Chlorine undergoes disproportionation in the reaction with cold dilute aqueous sodium hydroxide.
Define electronegativity
The tendency of an atom to attract a bonding pair of electrons in a covalent bond
Define oxidising ability
Oxidising ability is the ability to act as an oxidising agent. The oxidising ability of the halogens decreases down the group. This is because down the group the atoms get larger so the electrons are less strongly attracted to the nucleus so it’s harder to gain an electron.
Define reducing ability
Reducing ability is the ability to act as a reducing agent. The reducing ability, or reducing power, of the halides increases down the group. This is because to act as a reducing agent the halide needs to lose an electron. As you go down the group it is easier for a halide to lose an electron because the attraction from the outer electron and nucleus decreases due to increase shielding and an increasing ionic radius.
NaCl + H2SO4
Products: HCl
Reaction type: Acid-base
NaCl + H2SO4 -> NaHSO4 + HCl
Steamy Fumes
NaBr + H2SO4
Products: HBr
Reaction type: acid-base
NaBr + H2SO4 -> NaHSO4 + HBr
Steamy fumes
NaI + H2SO4
Products: HI
Reaction type: Acid-base
NaI + H2SO4 -> NaHSO4 + IH
Steamy fumes
2Br- + H2SO4
Products: SO2
Reaction type: reduction of H2SO4
2Br- + H2SO4 + 2H+ -> Br2 + SO2 + 2H2O
Colourless gas
2I- + H2SO4
Products: SO2
Reaction type: reduction of H2SO4
2I- + H2SO4 + 2H+ -> I2 + SO2 + 2H2O
Colourless gas
6I- + H2SO4
Product: yellow solid (S)
Reaction type: reduction of H2SO4
6I- + H2SO4 + 6H+ -> 3I2 + S + 4H2O
Yellow solid
8I- + H2SO4
Product: H2S
Reaction type: reduction of H2SO4
8I- + H2SO4 + 8H+ -> 4I2 + H2S + 4H2O
Bad egg gas
2I- + H2SO4
Products: I2
Reaction type: oxidation of I-
2I- + H2SO4 + 2H+ -> I2 + SO2 + 2H2O
Purple fumes
2Br- + H2SO4
Products: Br2
Reaction type: oxidation of Br-
2Br- + H2SO4 + 2H+ -> Br2 + SO2 + 2H2O
Brown fumes
What are the physical properties of fluorine?
Poisonous yellow gas
What are the physical properties of chlorine?
Poisonous, dense, yellow green gas
What are the physical properties of bromine?
Toxic, red brown, volatile liquid.
(Red brown vapour)
Why are the physical properties of iodine?
Shiny, grey black solid, sublime to form of violet vapour
What are the physical properties of astatine?
Rarest naturally occurring element (no stable isotopes).
May be dark and have a higher melting point that iodine .
Why do halogens exist as diatomic molecules?
They have a single covalent bond between atoms
How does bond enthalpy change with atomic number?
The mean bond enthalpy decreases as atomic number increases for chlorine, bromine and iodine.
How does the colour of group 7 elements change down the group?
The colour of the elements becomes darker
How does the atomic radius of group 7 elements change down the group?
The atomic radius increases (more shells)
How does the reactivity of group 7 elements change down the group?
The reactivity decreases (increase shielding)
