Group 7: Physical Properties Flashcards
The group 7 elements are called halogens
The halogens have uses in
chlorines uses
bromine
iodine
water purification and as bleaching agents (chlorine
flame-retardants and fire extinguishers
and as antiseptic and disinfectant agents
All halogens have distinct colours which get ……going down the group
darker
f2
cl2
br2
i2
at room temp colours and state
F2(pale yellow gas)
Cl2(green gas)
Br2 ( brown liquids)
I2(Grey / black solid gives off purple fume
Volatility refers to how easily
substance can evaporate
A volatile substance will have a low boiling point
Going down the group, the boiling point of the elements ……..which means that the volatility of the halogens ……….
increases
decreases
This means that fluorine is the most volatile and iodine the least volatile
Bond Strength
Halogens are ……………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 …………..
The bonding pair of electrons get further away from the halogen nucleus and are therefore ………………..
diatomic
increases
less strongly attracted towards it
covalent bond is formed by the orbital overlap of two atoms and the attraction of electrons towards the nuclei; the bigger the atom, the weaker the covalent bond
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
why
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
The bond strength of the halogen molecules ………………..going down the group
decreases
Halogens are non-metals and are diatomic molecules at room temperature
This means that they exist as molecules which are made up of two similar atoms, such as F2
The halogens are what structures and what bonds form
simple molecular structures with weak van der Waals’ forces between the diatomic molecules caused by instantaneous dipole-induced dipole forces
The more electrons there are in a molecule, the greater the instantaneous dipole-induced dipole forces
Therefore, the larger the molecule the stronger the
melting and boiling points ……….
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