Explain the nature of hydride compounds of group-$15$ elements. Explain the nature of oxide compounds of group-$15$ elements. Write a note on halide compounds of group-$15$ elements.

(N/A) All the elements of group-$15$ form hydrides of type $EH_3$ where $E=N, P, As, Sb$ or $Bi$.
On moving down the group,the stability of hydrides decreases i.e.,$NH_3$ is most stable while $BiH_3$ is least stable. This is due to decrease in the bond dissociation enthalpy of $E-H$ bond as a result of increase in atomic size of the element. Consequently,the reducing character of hydrides increases.
Reducing strength: $NH_3 < PH_3 < AsH_3 < SbH_3 < BiH_3$
Thermal stability: $NH_3 > PH_3 > AsH_3 > SbH_3 > BiH_3$
Thus,ammonia is a mild reducing agent while $BiH_3$ is a strong reducing agent.
The basicity of the hydrides decreases down the group. $BiH_3$ is least basic while $NH_3$ is most basic. The high basicity of $NH_3$ is due to high electronegativity and small size of nitrogen.
Order of basicity: $NH_3 > PH_3 > AsH_3 > SbH_3 \geq BiH_3$
Ammonia $(NH_3)$ exhibits hydrogen bonding both in solid and liquid state. Because of this,it has higher melting and boiling points than that of $PH_3$.
Order of boiling points: $BiH_3 > SbH_3 > NH_3 > AsH_3 > PH_3$
All the elements of group-$15$ form two types of oxides: $E_2O_3$ and $E_2O_5$. The oxide in the higher oxidation state of the element is more acidic than that of lower oxidation state. The acidic character decreases down the group.
The oxides of the type $E_2O_3$ of nitrogen and phosphorus are purely acidic,those of arsenic and antimony are amphoteric,and those of bismuth are basic.
The acidic strength of the trioxides and pentoxides decreases with the decrease in the electronegativity of the central atom.
Acidic Strength of trioxide: $N_2O_3 > P_2O_3 > As_2O_3$
Acidic Strength of pentoxide: $N_2O_5 > P_2O_5 > As_2O_5$
The elements of group-$15$ react with halogens to form two series of halides: $EX_3$ and $EX_5$. The pentahalides of nitrogen are not known due to the absence of $d$-orbitals in its valence shell. Pentahalides are more covalent than trihalides. This is due to the fact that in pentahalides,the $(+5)$ oxidation state exists while in trihalides,the $(+3)$ oxidation state exists. Since elements in the $(+5)$ oxidation state have more polarising power than in the $(+3)$ oxidation state,the covalent character of bonds is greater in pentahalides.
The trivalent halides except $BiF_3$ are covalent. $BiF_3$ is ionic. All the trihalides of these elements except those of nitrogen are stable. Amongst the trihalides of nitrogen,only $NF_3$ is stable.