In the borax bead test,which of the following compounds is formed?

Which of the following is the strongest Lewis acid?

Describe the physical properties of $B$ and $Al$.

Marine plants are an important source of which of the following?

Which of the following boron compounds is the hardest?

$X$ reacts with aqueous $NaOH$ to form $Y$ and releases $H_2$ gas. When the aqueous solution of $Y$ is heated at $323 \ K - 333 \ K$ and $CO_2$ gas is passed through it,it yields $Al_2O_3 \cdot xH_2O$ (often represented as $Al(OH)_3$) and $Z$. Heating $Z$ at $1200 \ ^\circ C$ gives $Al_2O_3$. Identify $X, Y,$ and $Z$.