Cure your inorganic phobia
Boron family
Some important points
1. B, Al, Ga, In, and Tl are the members of the iiiA group. Their general electronic configurations ns2 np1. B is a metalloid and the remaining are metals.
2. B and Al exhibit +3 oxidation state, because they do not show inert pair effect. Ga, In and Tl show +1 and +3 oxidation states due to inert pair effect. This effect increases from Ga to Tl. Therefore stability of +3 oxidation state decrease and stability of +1 oxidation state increase. Two electron pairs are found in the outermost shell of Ga, In and Tl, which do not participate in, bond formation.
3. Radius of Tl+ is almost the same as that of large alkali metals. Therefore its carbonate nitrate, sulphate, alum and cyanide are isomorphous with k+.
4. On going downward in a group basic character of hydroxides increases. Hydroxides of Al and Ga are amphoteric, whereas, indium hydroxide is basic.
5. When elements of iiiA group form trihalides, trihydride and trialkyl, the only six electrons are present in their valence shell and they act as Lewis acid by accepting one electron pair.
6. Bond length in boron trihalides is low, because boron accepts electron share from halogens from completely filled pp orbitals by back donation.
7. Boron is more thermoresistant than carborundum, whose melting point is high. Its crystalline form is very hard.
8. Non-crystalline form of boron is very reactive, whereas crystalline form is inert.
9. Reduction of metal oxide by aluminium is called aluminothermy.
10. Lewis character of BF3 is low because due to its small size back donation of electrons by fluorine occurs readily. Therefore the order of tendency of accepting electrons is
BF3 < BCL3 < BBr3 < BI3
11. Compounds of boron formed with hydrogen are called boranes, and all the boranes are electron deficient compounds.
12. Inorganic benzene i.e. borazine or borazole and benzene are isoelectronic.
13. Diborane is used as rocket fuel.
14. Structure of boron nitride is same as that of graphite that is why it is called inorganic graphite.
15. Borazole, which is as hard as diamond, is prepared by heating boron nitride. The hardness of some substances is in the following order. Diamond > Borazole >Carborundum >Corundum
16. The metal most abundantly found on earth is Al.
17. Al forms many double salts and gets dissolved in acids as well as bases.
18. Crystalline Al2O3 is a component of many precious stones. For example, ruby topaz, emerald and agate.
19. Alloys like duralumin and aluminium bronze are formed from Al.
20. Boron is found in nature as borax (Na2B4O7.10H2O), kernite (Na2B4O7.4H2O), and calamines (Ca2B6O11.5H2O).
21. Unrefined form of borax is called tincal.
22. B2F4, B2Cl4, B2Br4 are examples of diborane tetrahalides.
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