In the nitrogen family,the $H-M-H$ bond angle in the hydrides $MH_3$ gradually becomes closer to $90^o$ on going from $N$ to $Sb$. This shows that gradually:

The bond energies (in $kJ \ mol^{-1}$) of $N-H$,$P-H$,and $As-H$ are respectively:

Given below are the two statements: one is labeled as Assertion $(A)$ and the other is labeled as Reason $(R)$.
Assertion $(A)$: There is a considerable increase in covalent radius from $N$ to $P$. However,from $As$ to $Bi$,only a small increase in covalent radius is observed.
Reason $(R)$: Covalent and ionic radii in a particular oxidation state increase down the group.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following substances is ionic?

Which of the following exhibits the highest solubility in water?

Identify the compound in which phosphorus exists in the oxidation state of $+1$.