group 7, the halogens (3.2.3) in papers 1 & 3 Flashcards
inorganic chemistry
1
Q
what happens to the atomic radius when you go down group 7?
A
increases
2
Q
what happens to the electronegativity as you go down group 7?
A
- decreases
- as the halogen atom gets bigger, any bonding pair electrons gets further away from the nucleus and so is less strongly attracted towards it.
3
Q
state the appearance and state of fluorine, chlorine, bromine and iodine.
A
- F: very pale yellow gas
- Cl: greenish gas, colourless solution
- Br: red liquid, yellow solution
- I: grey solid, brown solution
4
Q
what happens to the bpt and mpt as you go down the group?
A
- decreases
- As the molecules become larger they have
more electrons and so have larger van der
waals forces between the molecules. As the
intermolecular forces get larger more energy has to be put into break the forces. This increases the melting and boiling points.
5
Q
what happens to the oxidising power as you go down group 7?
A
- increases
- they oxidise other elements and are reduced in the process.
- they become halides after they take 1 electron.
6
Q
what colours are present when a halogen gets displaced?
A
- The colour of the solution in
the test tube shows which free
halogen is present in solution.
Chlorine =very pale green
solution (often colourless),
Bromine = yellow solution
Iodine = brown solution
7
Q
which halogen is the most effective oxidising agent?
A
- chlorine
- it displaces bromine and iodine
- incoming electrons will experience less shielding
- its the smallest halogen which makes it easier for the nucleus to attract an electron
8
Q
what are halides?
A
- reducing agents
- 2X -> X2 + 2e-
9
Q
whats the trend in reducing capabilities of halides?
A
- reducing power increases down a group, fluoride being very weak and iodide being very strong.
- as the number of shells in the ion increases, there is more shielding so the electrons become less strongly held.
10
Q
how far can hallides reduce H2SO4?
A
- KF: cant
- KCl: cant
- KBr: SO2
- KI: SO2, S, H2S
