THE P BLOCK ELEMENTS By Tasneem Hussain
THE BORON FAMILY Group 13 or IIIA consists of 5 elements - B, Al, Ga, In, TI Outer shell electronic configuration - ns2 np1 Physical properties . Metallic character - increases from B to T Oxidation state - B and Al +3, Ga, In and TI+1 Relative Stability of M+ and M3
Atomic and ionic radius - atomic radius, ionic radius and density increases from B to Tl Melting and boiling point - melting point decreases from B to Ga and then increases. Boiling point decreases from B to Tl. Ionisation energy - The ionisation energy decreases down the group due to increase in size. First oxidation potential - Boron has low value of oxidation potential, the other elements of this group have high values of oxidation potential Chemical properties Pure crystalline boron is very unreactive. Finely divided amorphous boron is more reactive.
"Action of air : 4M + 302--> 2M,03 Action of nitrogen 2M + N2 --> 2MN Action of halogen: 2M + 3X2 --> 2MX3 Action of acids : 2M 6H+ --> 2M3 3H2 2Al 6H2SO4 Al2(SO4)3 3SO2 6H20 . Action of alkalies 2M 2NaOH 6H2O 2Na+IM(OH)1 3H2 Only B,Al and Ga react with alkali.
General characteristics of the compounds of group 13 elements Boron forms hydrides of type - B,Hn+4 and BnH,+6 called boranes BX3 is electron deficient - Lewis acid BX3 Lewis acid +:NH3 lewis base -> [HzN -> BX3l -B also forms dihalides, BX. Lewis acid character - BF3<BCl3<BBr3 Anomalous Behavior of Boron 1. Non - metal 2. Bad conductor of electricity
3. Boron exhibits allotrophy. 4. Forms only covalent compounds. 5. Hydroxides and oxides are acidic in nature. 6. Trihalides of boron exist as monomer. 7. Borates are more stable than aluminates. 8. Maximum covalency 4 BH4 ion while other members exhibit a maximum valency of six [Al(OH)613- 9. Boron does not decompose steam. 10.B3HNO-H BO 3NO 11.Boron carbide is hardest known artificial substance - Norbide. 12.Boron carbide (BAC) is even harder than carborundum
Boric acid (H3BO3) or orthoboric acid Preparation 1. From borax - (Na,BO7.10H,O): Na2B407 2HCI 5H20 2NaCl + 4B(OH) Properties 2. Action of heat H3B0,--> HBO2--> H, B40,--> B203 2 3 373K 433K Red hot 2. Boric acid behave as weak monobasic acid.
Uses 1. Used as antiseptic,eye wash and food preservative. 2. Used in preparation of glass,glazes and enamels. 3. Used in leather industry.
Persuing MBBS from PCMS AND RC Bhopal Find Quiz based on previous years papers of NEET, AIIMS and AIPMT on my feed.