Group 7 Flashcards
Explain the trend in electronegativity as you go down group 7.
Electronegativity decreases as you go down group 7 because size of atoms increase. Their atomic radius is greater and there is more shielding. Therefore the greater nuclear charge has no great effect.
Explain the trend in boiling point as you go down group 7.
As you go down the size of each atom increases and therefore there are more van der waals forces. Therefore more energy is required to break the bonds.
What type of molecules are halogens ?
Simple, diatomic covalent molecules.
What colour are each of the halogens in pure form ?
Fluorine - pale yellow has
Chlorine - pale green has
Bromine - dark red liquid
Iodine - grey solid
Outline the physical properties of each of the halogens in non-polar solvents.
Fluorine- reacts with solvents
Chlorine - pale green solution
Bromine - orange solution
Iodine - purple solution.
Outline the physical properties of the halogen in water.
Fluorine - reacts with water
Chlorine- pale green solution
Bromine - orange solution
Iodine - insoluble. But forms a brown solution if excess KCl is present.
Describe the physical properties of astatine at room temperature.
Black solid
Why do we rarely experiment with astatine ?
It is highly radioactive so is unstable.
Describe the trends in ionisation energy as you go down group 7.
Ionisation energy decreases. The atomic radius of each atom increases and there is more shielding so the attraction of the nucleus to the outer electrons is less.
Describe the polarity of halogens ?
Non-polar
What property of halogens means they dissolve well in nonpolar solvents.
Halogens are non-polar
Describe the trends in oxidising power of halogens as you go down group 7.
Oxidising power decreases. It is therefore more difficult for iodine to accept electrons than fluorine. The smaller atoms can attract electrons more easily with their nuclear charge as they have less shielding.
What colour are halide ions ?
Colourless
When can a displacement reaction with halogens not occur.
When the diatomic halogen molecules is lower in the group (less reactive) than tha halide ion.
What charge do halide ions have ??
-1
Describe the trend in reducing ability of halide ions as you go down the group.
As you go down group 7 reducing ability increases because atomic radius of each atom increasss so the electron being lost isn’t held as strongly to the nuclear charge and can be easily lost.
What affect does sodium chloride have on concentrated sulphuric acid ??
No reactions can occur because chlorine has a low reducing power.
What affect does sodium bromine have on concentrated sulphuric acid ??
Bromine can reduce sulphuric acid to sulphur dioxide.
You get: Br2, SO2
What affect does sodium iodide have on concentrated sulphuric acid ??
Sodium iodidide can reduce the sulphuric acid to sulphur dioxide, hydrogen sulphide and solid sulphur because it can donate electrons easily.
What substance is used to identify halides ?
Acidified silver nitrate.
What colour precipitate does silver chloride form in water and why ?
White
It has a low solubility in water
What are the products of each halide ion in acidified silver nitrate ?
Fluoride - colourless
Chloride - white
Bromide - yellow
Iodide -Colourless
Describe the products form for each halide ion in dilute NH3
Chloride - soluble
Bromide - partly soluble
Iodide - insoluble
Describe the products form for each halide ion in concentrated NH3
Chloride - soluble
Bromide - soluble
Iodide - insoluble
Why can’t hydrochloride acid be used to identify halide ions ?
A white precipitate will be formed giving a false positive.
Why is the silver nitrate solution acidified.
It allows an acid base faction which removes carbonate ions which could interfere with the silver nitrate test.
Why does HF have an exceptionally high boiling point ?
Because it has hydrogen intermolecular bonding.
What are the uses of chlorine ?
Kills bacteria in drinking water and swimming pools. Bleach
Write the reaction of chlorine with water.
Cl2(g) + H2O(l) — HClO(aq) + HCl(aq)
What type of reaction is the reaction of chlorine with water.
Disporportiination
What is chloric1acid used for ?
Oxidising agent which sterilised water.
Why can chlorine gas be used to sterilise water despite being toxic.
Used in low dosage.
What is the equation for chlorine reacting with an alkali ?? (Sodium hydroxide )
Cl2 (g) + 2NaOH(an) - NaClO(an) + NaCl(an) +H2O(l)
What type of reaction is the equation for chlorine reacting with an alkali ?? (Sodium hydroxide )
Disproportionation