Chemistry AQA AS Unit 2 Group 7

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

Hide resource detailsShow resource details Download Chemistry AQA AS Unit 1 Periodicity (Word Document 36.87 Kb.)

Share:

HideShow resource information
  • Created by: Chelcie
  • Created on: 02-09-13 13:34
Preview of Chemistry AQA AS Unit 2 Group 7

First 343 words of the document:

Group 7, the Halogens
PHYSICAL PROPERTIES
Fl ­ pale yellow gas
Cl ­ greenish gas
Br ­ red brown liquid
I ­ black solid
`Swimming bath smell'
F ­ F bond is weak as the small size of the atom leads to repulsion between the non bonding
electrons.
SIZE OF ATOMS
Get bigger down the group as the elements going down have an extra filled main level of electrons.
ELECTRONEGATIVITY
Electronegativity is the measure of ability of an atom to attract electrons, or an electron density,
towards itself within a covalent bond.
It depends on the attraction between the nucleus and the bonding electrons in the outer shell.
Electronegativity decreases down the group as the extra filled main level, increasing the size of the
atom, providing increased shielding, lessens the attraction between the electrons and the nucleus.
MELTING AND BOILING POINTS
Increase down the group. This is because the larger atoms have more electrons; this makes the
V.D.W. forces between the molecules stronger.
The lower the boiling point, the more volatile the element.
TRENDS IN OXIDISING ABLILITY
Halogens usually react by gaining electrons to become negative ions with a charge of -1. So these
reactions are redox reactions.
Cl + 2e 2Cl
The oxidising ability of the halogens decreases as we go down the group.
DISPLACEMENT REACTIONS
Halogens will react with metal halides in a solution by displacing a less reactive halogen.
Cl (aq) + 2NaBr (aq) Br (aq) + 2NaCl (aq)
(Sodium ions are spectator ions)
THE OXIDATION OF A HALIDE BY A HALOGEN IS THE BASIS OF A METHOD FOR EXTRACTING
BROMINE FROM SEA WATER.
Cl (aq) + 2Br (aq) Br (aq) + 2CL (aq)
Iodine was discovered by extracting it from kelp which is obtained by burning seaweed. Salts are
removed from the kelp by washing with water. Residue is heated with manganese dioxide and
concentrated SO. 2I + MnO Mn2+ + 2HO + I

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Potassium Chloride Potassium Bromide Potassium Iodide (aq)
(aq) (aq)
Chlorine Water N/A Brown colour Dark brown
Bromine Water No reaction N/A Dark brown
Iodine Solution No reaction No reaction N/A
HALIDE IONS AS REDUCING AGENTS
Halide ions give away/lose es and become halogen molecules.
Increases reducing power down the group as the larger the ion, the more easily it loses an e.
THE REACTIONS OF SODIUM HALIDES WITH SO
SODIUM CHLORIDE (SOLID)
Drops of concentrated sulphuric acid are added to solid sodium chloride.…read more

Page 3

Preview of page 3

Here's a taster:

IDENTIFYING METAL HALIDES WITH SILVER IONS
Before testing for halide ions you have to remove carbonate and hydroxide impurities as
silver carbonate and silver hydroxide are both insoluble precipitates.
Therefore nitric acid is added first to remove them as you convert them into soluble things.…read more

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »