Biology Topic 6
Noble Gases
Located in group 0
Colourless gases.
Low melting and boiling points.
Low density.
Poor conductors of heat and electricity.
As you go down the melting point and boiling point increase.
As you go down the density increases.
Chemically inert, they are non reactive.
The atoms have full outer shells
Makes it difficult for them to gain, lose or share electrons.
They have stable electronic configuration so they are unreactive.
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Uses of Noble Gasses
Helium - Low density and is non-flammable. Used to fill weather balloons and airships.
Neon gives a red-orange light when electricity is passed through, used for advertising
Argon is used for lamps because it's inflammable and is inert.
Halogen Reactivity
The reactivity of the halogens decreases down the group from fluorine to iodine
This is a displacement reaction to where the more reactive element replaces the less reactive element
There are 7 electrons in the outer shell of each atom
As you go down group 7 it becomes more difficult for the atoms to form a negative ion because the atom sizes get bigger as you go down. Because of this, the attraction between the nucleus and the incoming electrons decreases, making it harder to capture the electron.
Group 1 - Alkali Metals
Relatively low melting points
soft enough to be cut with a knife
Very reactive and the reactivity increases down the group
All the metals produce hydrogen gas
One electron on the outer shell when the alkali metal reacts they give one electron from their outer shells and so becomes a positive ion.
As you go down group 1 the reactivity increases because there is less energy needed to remove the electron