question_answer

Aluminium forms \[{{[Al{{F}_{6}}]}^{3-}}\] ion but boron does not form \[{{[B{{F}_{6}}]}^{3-}}\] ion. Explain.

Answer:

                Boron can show a maximum valency as well as co-ordination number of four. Therefore, it cannot form \[{{[B{{F}_{6}}]}^{3-}}\] ion where it is to exhibit co-ordination number six. On the other hand, aluminium can extend its valency as well as co-ordination number to six due to the presence of vacant 3d orbitals. Therefore, it can form \[{{[Al{{F}_{6}}]}^{3-}}\] ion.