Group 7 Flashcards
What are group 7 elements called
Halogens
What are the uses of halogen
water purification and as bleaching agents (chlorine)
As flame-retardants and fire extinguishers (bromine)
as antiseptic and disinfectant agents (iodine)
Fluorine state at room temperature
Chlorine is pale and colourless and gas
Chlorine state at room temperature
Green/yellow gas
Bromine state at room temperature
Orange/brown liquid
Iodine state at room temperature
Grey/black solid purple vapour
What is volitility
Volatility refers to how easily a substance can evaporate
A volatile substance will have a low boiling point
What is the boiling point of the elements down the group
The boiling point of the elements increases which means that the volatility of the halogens decreases
This means that fluorine is the most volatile and iodine the least volatile
Bond strength in halogens
Halogens are diatomic molecules in which covalent bonds are formed by overlapping their orbitals
In a covalent bond, the bonding pair of electrons is attracted to the nuclei on either side and it is this attraction that holds the molecule together
Going down the group, the atomic size of the halogens increases
The bonding pair of electrons get further away from the halogen nucleus and are therefore less strongly attracted towards it
What is bond enthalpy
Bond enthalpy is the energy needed to break one mole of covalent bonds
The higher the bond enthalpy, the stronger the bond
An exception to this is fluorine which has a smaller bond enthalpy than chlorine and bromine
Fluorine is so small that when two atoms of fluorine get together their lone pairs get so close that they cause significant repulsion counteracting the attraction between the bonding pair of electrons and two nuclei
What structures are the halogens
The halogens are simple molecular structures with weak van der Waals’ forces between the diatomic molecules caused by instantaneous dipole-induced dipole forces
Why do melting and boiling points increase down the group
The more electrons there are in a molecule, the greater the instantaneous dipole-induced dipole forces
Therefore, the larger the molecule the stronger the van der Waals’ forces between molecules
This is why as you go down the group, it gets more difficult to separate the molecules and the melting and boiling points increase
As it gets more difficult to separate the molecules, the volatility of the halogens decreases going down the group
