Explain the following:
$(1)$ $BF_3$ does not hydrolyze.
$(2)$ Why does the element silicon not form a graphite-like structure,whereas carbon does?

(N/A) $(1)$ $BF_3$ undergoes partial hydrolysis. The $HF$ produced reacts with $H_3BO_3$ to form fluoroboric acid,preventing complete hydrolysis:
$4BF_3 + 3H_2O \rightarrow H_3BO_3 + 3H^+ + 3[BF_4]^-$
$(2)$ In graphite,carbon atoms are $sp^2$ hybridized and form $p\pi-p\pi$ double bonds due to their small size and high electronegativity. Silicon,due to its larger atomic size and lower electronegativity,cannot form stable $p\pi-p\pi$ multiple bonds,and therefore cannot form a graphite-like structure.