Kernite and cryolite are the minerals of two elements $X$ and $Z$. Respectively $X$ and $Z$ are

Which of the following represents the structure of inorganic benzene?

Boron does not form $B^{3+}$ cation easily. It is due to

The type of hybridisation of boron in diborane is

In the reactions $I$ and $II$,the covalencies of $Be$ and $Al$ in $X$ and $Y$ are respectively:
$I$ $Be(OH)_2 + NaOH \text{ (excess)} \rightarrow X$
$II$ $Al(OH)_3 + NaOH \text{ (excess)} \rightarrow Y$

Identify the correct statements about Boron.
$I.$ It has a high melting point.
$II.$ It has a high density.
$III.$ It has high electrical conductivity.
$IV.$ The $^{10}B$ isotope of it has a high ability to absorb neutrons.