The number of acidic protons in $H_{3}PO_{3}$ is:

Orthoboric acid in aqueous medium is

Which of the following types of hybridization occurs in diborane $(B_2H_6)$?

Identify the correct statements from the following:
$(i)$ The atomic radius of $Al$ is lower than the atomic radius of $Ga$.
$(ii)$ Boron exists in many allotropic forms.
$(iii)$ The melting point of $Ga$ is lowest among the group $13$ elements.

For a $p$-block element,its $3d, 3s, 3p$ and $4s$ orbitals are completely filled and the differentiating electron goes to the $4p$ orbital. The element should have its atomic number in the range:

When metal $X$ is treated with sodium hydroxide,a white precipitate $(A)$ is obtained,which is soluble in excess of $NaOH$ to give soluble complex $(B)$. Compound $(A)$ is soluble in dilute $HCl$ to form compound $(C)$. The compound $(A)$ when heated strongly gives $(D)$,which is used to extract metal. Identify $(X), (A), (B), (C)$ and $(D)$. Write suitable equations to support their identities.