Group 13 elements - The Boron family
The group 13(IIIA) elements are Boron, aluminium, gallium, indium and thallium.
1. Boron is a relatively rare element, accounting for only about 0.001% of the earth's crust by mass.
2. Aluminium is the most important of 13th group elements.
3. Gallium is remarkable for its unusually low melting point (29.7 o C) and therefore generally exist as a liquid at room temperature. Its most important use is in making gallium arsenide. This is a semi conductor material employed in the manufacture of diode lasers for laser printers, compact -disc players and fibre optic communication devices.
4. Indium is also used in making semi conductor devices, such as transistors and electrical resistance thermometers called thermistors.
5. Thallium is extremely toxic and has no commercial use.
Electronic configurations: The general electronic configuration of the various elements of this family is ns2 np1.
Electronic configuration of group 13 elements
Atomic Number: 5 Electronic Configuration : [He] 2s2 2p1 Group Number : 13 Period Number : 2
Atomic Number: 13 Electronic Configuration : [Ne] 3s2 3p1 Group Number : 13 Period Number : 3
Atomic Number: 31 Electronic Configuration : [Ar] 3d10 4s2 4p1 Group Number : 13 Period Number : 4
Atomic Number: 49 Electronic Configuration : [Kr] 4d10 5s2 5p1 Group Number : 13 Period Number : 5
Atomic Number: 81 Electronic Configuration : [Xe] 4f14 5d10 6s2 6p1 Group Number : 13 Period Number : 6
Potash Alum, K2 SO4. Al2 (SO4)3. 24 H2O
Potash Alum is manufactured from alunite or alum stone.
From Alunite: Alunite or alum stone is K2SO4. Al2(SO4)3. 4Al(OH)3. It is finely powdered and boiled with dilute sulphuric acid, the aluminium hydroxide part changes into aluminium sulphate. When a little more potassium sulphate in calculated amount is added, the alum is crystallised.
1. Potash alum is a white crystalline solid.
2. It is soluble in water but insoluble in alcohol.
3. The aqueous solution is acidic due to the hydrolysis of Al2 (SO4)3.
4. When heated, it melts at 365K and on further heating loses the whole of its water of crystallisation and swells up. The swollen mass so produced is called burnt alum.
1. It is used in purification of water, water proofing of textiles and in dyeing and paper industry.
2. It is also employed to arrest bleeding.