The halogens
Physical properties:
Þ the halogens are diatomic
Element State Colour Colour of vapour
I 2
Fluorine Gas Pale yellow -
Chlorine Gas Green -
Bromine Liquid Brown Brown
Iodine Solid Grey Purple
Reactivity:
Þ The halogens react by gaining an electron to form 1– Melting
halide ions
Reactivit point
Þ Reactivity decreases down the group because: y
* Atomic radius increases down the group
* The number of electrons increases down
the group
* The number of shells increases down the
Þ This decreases
group the attraction of the nucleus towards electrons due
to electron shielding and the outer shell being further from the nucleus
Melting/Boiling points:
Þ Melting/boiling is caused by intermolecular forces being overcome
by thermal energy
Þ Melting/boiling points increase going down the group because:
* The number of electrons increases down the
group
* Thisthermal
Þ More makes energy
the induced
is dipole-dipole forces
needed to overcome these
Physical properties:
Þ the halogens are diatomic
Element State Colour Colour of vapour
I 2
Fluorine Gas Pale yellow -
Chlorine Gas Green -
Bromine Liquid Brown Brown
Iodine Solid Grey Purple
Reactivity:
Þ The halogens react by gaining an electron to form 1– Melting
halide ions
Reactivit point
Þ Reactivity decreases down the group because: y
* Atomic radius increases down the group
* The number of electrons increases down
the group
* The number of shells increases down the
Þ This decreases
group the attraction of the nucleus towards electrons due
to electron shielding and the outer shell being further from the nucleus
Melting/Boiling points:
Þ Melting/boiling is caused by intermolecular forces being overcome
by thermal energy
Þ Melting/boiling points increase going down the group because:
* The number of electrons increases down the
group
* Thisthermal
Þ More makes energy
the induced
is dipole-dipole forces
needed to overcome these
