chem - groups in a periodic table (6)

• Alkali metals are soft and have relatively low melting points.
• Lithium, sodium and potassium in group one react vigorously with water to create an alkaline metal hydroxide and hydrogen.
• Down the group in alkali metals, it is easier to lose electrons and form cations.
• Chlorine is a yellow-green gas, bromine is a red-brown liquid, and iodine is a purple solid.
• There is a trend in state from gas to liquid to solid down group 7.
• The melting and boiling points increase as you go down the group in halogens.
• From this, you can predict that any halogens above chlorine will be gases, and any below iodine will be solids.
• When damp litmus paper is put into chlorine gas, the litmus paper is bleached and turns white.
• The halogens, chlorine, bromine and iodine, react with metals to form ionic compounds in which the halide ion carries a -1 charge.
• Reaction is less vigorous as you move down group 7, but they still all react to form metal halides.
• The halogens form halides which dissolve in water and are acidic solutions.
• A more reactive halogen can displace a less reactive in an aqueous solution of its salt.
• Chlorine will displace bromine and iodine, bromine will displace iodine but not chlorine, and iodine cannot replace either.
• As you go down the group in halogens, the reactivity decreases.
• The halogens react by gaining an electron in their outer shell, as you go down the group.
• More reactive halogen which displaces the less reactive one, forms a negative ion itself, therefore being reduced as it has gained electrons.
• The less reactive halogen that is displaced is oxidised as it loses these electrons to go from a negative ion to an atom with 0 charge.
• The electronic configurations of the halogens are: fluorine: 2,7, chlorine: 2,8,7.
• These show clearly the extra shell of electrons gained as you move down group 7.
• Noble gases are chemically inert because they have 8 electrons in their outer shell (except helium, which has 2- but this shell is still full).
• Their electronic configurations demonstrate their full outer shells, and this makes them unreactive because they are very stable.
• Low density makes helium used in balloons and airships, as it is less dense than air, so balloons float upwards.
• Inertness and non-flammability make argon, krypton and xenon used in light bulbs, as they stop filament burning away.
• Inertness makes argon used as a shield gas during welding, as it is denser than air which keeps it away from the metal.
• The boiling points of the noble gases increase with increasing RAM (going down the group).
• The densities of the noble gases increase as you go down the group.