diborane B2H6 , is simplest boron hydride
• Structure : three-center two-electron : the H atoms are simultaneously bonded to two B atoms the B-H bridging bond lengths are greater than B-H terminal .
• - Boron oxide is acidic ( it reacts readily with water to form boric acid )
• aluminium compounds : aluminium oxide is amphoteric
• aluminum halides , e . g ., AlCl3 is dimer , an important catalyst in organic chemistry have an incomplete octet , acts as Lewic acid by accepting lone pairs from Lewic bases , forming adduct
• aluminum hydride , e . g ., LiAlH4 , a reducing agent
• Atomic Properties - Electronic Configurations
Element Symbol Atomic Electronic Abundance in Earth ’ s No . Configuration Crest ( in ppm )
Boron |
B |
5 |
[ He ] 2s 2 2p 1 |
8 |
Aluminium Al |
13 |
[ Ne ] 3s 2 3p 1 |
81,300 |
Galium |
Ga |
31 |
[ Ar ] 3d 10 4s 2 4p 1 |
15 |
Indium |
In |
49 |
[ Kr ] 4d 10 5s 2 5p 1 |
1 |
Thallium |
Tl |
81 |
[ Xe ] 5d 10 6s 2 6p 1 |
0.3 |
Atomic and ionic radii
• The atomic and ionic radii of group 13 elements are compared to corresponding elements of group 2 . From left to right in the period , the magnitude of nuclear charge increases but the electrons are added to , the same shell . These electrons do not screen each other , therefore , the electrons experience greater nuclear charge .
• In other words , effective nuclear charge increases and thus , size decreases . Therefore , the elements of this group have smaller size than the corresponding elements of second group .
• On moving down the group both atomic and ionic radii are expected to increase due to the addition of new shells . However , the observed atomic radius of Al ( 143 pm ) is slightly more than that of Ga ( l35 pm ).