Group 7 - The Halogens Flashcards
What is the colour and state of fluorine at room temperature
Pale yellow gas
What is the colour and state of bromine at room temperature
Brown liquid
What is the colour and state of chlorine at room temperature
Pale green gas
What is the colour and state of iodine at room temperature
Dark grey solid
What is the colour and state of astatine at room temperature
Black solid
What does iodine sublime to give
A purple vapour
Describe and explain the trend in boiling points as you go down group 7
The boiling points increase because the number of electrons increases as you go down the group which increases the uneven distribution of electrons. The van der vaals forces become stronger as you go down the group, so more energy is needed to break the stronger intermolecular forces.
Why does bromine have a higher boiling point than chlorine
Bromine has more electrons than chlorine, so the Van der Vaals forces are stronger in bromine. More energy is needed to break the stronger intermolecular forces in bromine.
What is the trend in solubility of the halogens as you go down the group
Solubility in water decreases down the group.
The complex ion I3- is more soluble in water than iodine. Explain this.
Iodine molecules are non-polar and thus have no charge, whereas the I3- ion is negatively charged and will therefore be attracted to the delta positive H atom in a water molecule.
Describe and explain the trend in electronegativity as you go down group 7
As you go down the group, electronegativity decreases, because as you go down the group the atom gets larger since the atomic radii increases due to increased number of shells. The nucleus is therefore less able to attract the bonding pair of electrons.
Describe and explain the trend in oxidising ability as you go down group 7
The oxidising ability decreases as you go down the group because the atom gets bigger as it has more shells. There is now a weaker force of attraction between the positive nucleus and the incoming electron in the bigger atom, so the ability to gain an electron is more difficult as you go down the group.
Why is chlorine a stronger oxidising agent than bromine
The chlorine atom is smaller than a bromine atom as it has fewer electrons shells. There is a stronger force of attraction between the positive nucleus and the incoming electron in chlorine than in bromine, so the ability to gain an electron is easier in chlorine.
Oxidising agents
Electron acceptors
What will a halogen which is a stronger oxidising agent do when it reacts with a compound containing a halogen with a weaker oxidising power
It will displace that weaker halogen
Cl2(aq) + 2KBr(aq) →
Br2(aq) + 2KCl(aq)
the solution turns orange because bromine is displaced.
If a displacement reaction does not take place in dilute solution at room temperature, give 2 suggestions as to how the conditions could be changed so the reaction may occur
Increase the concentration of the solutions
Warm the solutions
Suggest why fluorine can’t form FO2- but chlorine can form ClO2-
Fluorine has no 2d orbitals, so cannot expand its octet. Therefore fluorine can only form one covalent bond. A 3p electron in a chlorine atom is promoted into an empty 3d orbital, so chlorine can form 3 covalent bonds.
