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).