Question

What happens to the following properties of group 15 hydrides as we move down the group?

1. Basic Character
2. Thermal stability
3. Reducing nature
4. Dipole moment
5. Bond angle

Answer 1

$\left)1\right)$ Basic character decreases from ${NH}_3$ to ${BiH}_3$ because as the size of central atom increases, electron density on central atom decreases and hence its ability due donate pair of electron decreases and thus its basic character decreases from ${NH}_3$ to ${BiH}_3$.

$\left(2\right)$ Thermal stability decreases $\to$ Thermal stability $\alpha \frac{1}{sizes}$ so as size of central atom increases, so stability decreases.

$\left(3\right)$ Reducing nature increases $\to$ As the stability of hydride decreases down the group its reducing power increases.

$\left(4\right)$ Dipole moment decreases $\to$ As the electronegativity of the central atom decreases down the group, the dipole moment of hydrides of these elements decreases.

$95)$ Bond angle decreases $\to$ The hydrides of these elements are pyramidal in shape with a lone pair of electrons in one of the orbitals. On moving down the group the bond angles gradually decrease due to a decrease in bond pair-bond pair repulsion.