# Which of the following facts regarding boron and silicon is not true ?

$\begin {array} {1 1} (A)\;\text{Boron and silicons are semiconductors} \\ (B)\;\text{Boron and silicons form halides which are not hydrolysed} \\ (C)\;\text{Boron and silicon react with magnesium to form magnesium boride and magnesium silicide which are decomposed by acids to give volatile borane and silane, respectively.} \\ (D)\;\text{Both Boron and silicon react with alkalis to form borates and silicates containing$BO_4$and$SiO_4$tetrahedral units, respectively.} \end {array}$

The halides of B and Al are hydrolysed.
$BCl_3+3H_2O \rightarrow B(OH)_3 ( Boric \: acid ) + 3HCl$ and $SiCl_4+4H_2O \rightarrow Si(OH)_4 (Silicic\: acid ) +4HCl$
Hence (B) is the correct answer.
Boron and silicons form halides which are not hydrolysed
edited Jul 28, 2014