Group 7 Flashcards
The elements in group 7 are called
Halogens
The halogens are all
Toxic. Cl is used to sterilize drinking water and water in swimming pools. Iodine is useful in antiseptics and to treat wounds
List the halogens (5)
F
Cl
Br
I
At
Common properties in halogens
- non metals
- low m.p and b.p
- brittle when solid
- poor conductors of heal/electricity
- coloured vapours
- they are diatomic
M.p / B.p
They have low m.p/b.p as it is a typical property of non metals
Fluorine, at the top of group 7 has the lowest m.p/b.p in the group. The m.p/b.p then increase as you go down the group
Atomic radius
Increases down the group as the atoms are becoming larger, Thus the size of the molecules are also increasing, so too does the amount of van-der-waals forces. Thus the m.p and b.p increases
Colour
The halogens become darker as you go down the group
Colour of F
pale yellow
Colour of Cl
yellow-green
colour of Br
red brown
Colour of I2
Shiny-purple- black but easily turn into a dark vapour whne heated
Density
increased won the group as the halogens change from the gaseous state into solid. Thus the halogens are becoming more dense as the group is descended as the states are changing
Ease of ionisation/reactivity
The halogens are non-metal, they they would ionise or form ions by gaining electrons. As the group decends, the atomic radius of the halogens are increasing and as a result, the valence electrons are coming further removed from the nucleus. As the halogens atomic radius increases, the nucleus is less able to attract electrons and as such, ionisation becomes increasingly difficult. Thus the halogens are becoming less reactive as the group descends
A more reactive halogen
can displace a less reactive halogen from its salt dissolved in water eg. displacement of bromine from sodium bromide
(read displacement note)
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