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The p-Block Elements — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryThe p-Block Elements2 Marks
Question
Explain the following:
Aluminium forms $\left[\mathrm{AlF}_6\right]^{3-}$ ion but boron does not form $\left[\mathrm{BF}_6\right]^{3-}$ ion.
✓

Answer

Al has vacant d-orbitals and hence can expand its coordination number from 4 to 6 and hence forms octahedral $\left[\mathrm{A}_1 \mathrm{~F}_6\right]^{3-}$ ion in which Al undergoes $\mathrm{sp}^3 \mathrm{~d}^2$ hybridisation. In contrast, B does not have d -orbitals. Therefore, it can have a maximum coordination number of 4 . Therefore, B forms $\left[\mathrm{BF}_4\right]^{-}$(in which B is $\mathrm{sp}^3$-hybridised) but not $\left[\mathrm{BF}_6\right]^{3-}$.

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