Typical Exam Questions!!!!(STR/ESSAY)
Group I ( alkali metals)
It is known as alkali metals because it reacts with water to form HYDROXIDES and hydrogen gas.
They are soft, low densities ( hence can be cut by knife ), having charges (+1) and the melting point decreases down the group. They are very reactive hence they need to be stored under oil to prevent reaction with air and water.
An Easy Way For Pupils To Remember the reactivity.......
'F' is the MOST REACTIVE !!!!!
For group I, Francium is the most reactive!!!! ( hence reactivity increases down the group )
Pupils are required to state the way the element react with water!!!!
Lithium reacts fast.
Sodium reacts quickly, catches fire sometimes explodes
Potassium reacts EXTREMELY FAST; catches fire and then EXPLODES.
As for rubidium, caesium and francium.... the reactivity will be explosion because they are more reactive than potassium.
Group VII ( halogen)
Each molecule is diatomic (F2, Cl2, Br2, I2, At2), having charges of (-1) and the boiling points increases down the group. They are very reactive and react VIGOROUSLY with metals to form ionic salts. Reactivity decreases down the group.
Remember: F is the most reactive.
Hence Fluorine is the most reactive, followered by chlorine, bromine, iodine and the least reactive is astatine.
As for the colours, it darkens down the group.
Fluorine is light yellow
Chlorine is yellow green
Bromine is brown
Iodine is dark purple ( black is acceptable)
Astatine is black
Since the boiling points increases down the group, the states are as follows:
Fluorine-(gas)
Chlorine-(gas)
Bromine-(liquid)
Iodine-(solid)
Astatine-(solid)
Since reactivity decreases down group 7, A MORE REATIVITY HALOGEN WILL BE ABLE TO DISPLACE A LESS REACTIVE HALOGEN FROM AN AQUEOUS SOLUTIONS OF ITS SALT.
This means that fluorine is able to displace (kick out) all the rest of the elements from group 7:
F2 (g) + 2 NaCl(aq) ----> 2 NaF(aq) + Cl2(aq)
However, a less reactive halogen will not be able to displace a more reactive halogen:
Cl2(g) + NaF (aq) ---> no reaction
GROUP 8 ( NOBLE GASES )
These elements are not able to combine with other atoms because of its stable electronic configuration ( octet structure can be used to replace 'stable-electronic configuration').
Hence group 8 elements are MONOATOMIC.
Pupils will need to know the uses:
Helium-hot air balloon
Neon- advertising lights
Argon / Neon - in light bulbs
Argon - manufacturing of steel ( flush air from molten steel to protect it from further reaction of the air )
