Question

"Alkali metal hydrides are ionic in nature."
Answer whether the above statement is true or false.
If true enter 1, else enter 0.

Answer 1

The alkali metals are highly hydrated. The smaller the size of the ion, the greater is the degree of hydration. Thus, $L{i}^{+}$ ion gets much more hydrated than $N{a}^{+}$ ion which in turn is more hydrated than $K^{+}$ ion and so on.

The extent of hydration decreases down the group. As a result of larger hydration, $L{i}^{+}$ ion than $N{a}^{+}$, the effective size of $L{i}^{+}$ ion is more than that of $N{a}^{+}$ion. Further the ionic radii in water called hydrated ionic radii it is decreases. As a result, the hydrated $L{i}^{+}$ ion is being largest ionic size has the lowest mobility in water. On the other hand, the hydrated $C{s}^{+}$ ion being smallest in size has the highest mobility in water.

$L{i}^{+}>N{a}^{+}>K^{+}>R{b}^{+}>C{s}^{+}$