Group 7: Physical Properties

Question 1

The group 7 elements are called halogens
The halogens have uses in
chlorines uses

bromine

iodine

Answer 1

water purification and as bleaching agents (chlorine

flame-retardants and fire extinguishers

and as antiseptic and disinfectant agents

Question 2

All halogens have distinct colours which get ……going down the group

Answer 2

darker

Question 3

f2

cl2

br2

i2

at room temp colours and state

Answer 3

F2(pale yellow gas)

Cl2(green gas)

Br2 ( brown liquids)

I2(Grey / black solid gives off purple fume

Question 4

Volatility refers to how easily

Answer 4

substance can evaporate
A volatile substance will have a low boiling point

Question 5

Going down the group, the boiling point of the elements ……..which means that the volatility of the halogens ……….

Answer 5

increases

decreases

This means that fluorine is the most volatile and iodine the least volatile

Question 6

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 ………………..

Answer 6

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

Question 7

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

Answer 7

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

Question 8

The bond strength of the halogen molecules ………………..going down the group

Answer 8

decreases

Question 9

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

Answer 9

simple molecular structures with weak van der Waals’ forces between the diatomic molecules caused by instantaneous dipole-induced dipole forces

Question 10

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 ……….

Answer 10

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

Question 11

As it gets more difficult to separate the molecules, the volatility of the halogens

Answer 11

decreases going down the group