Write a note on interstitial compounds.
Interstitial compounds are those which are formed when small atoms like $B$, $H$, $C$ or $N$ are trapped inside the crystal lattice of metals.
The transition elements form interstitial compounds with these elements. The $B$, $H$, $C$ and $N$ occupy the vacant spaces in the crystal lattice and as a result, the compounds formed are extremely hard.
They are classified as borides, hydrides, carbides or nitrides depending on nature of atoms trapped in the vacant sites. They are usually non-stoichiometric, neither typically covalent nor ionic. Ex. : $\mathrm{TiC}, \mathrm{Mn}_{4} \mathrm{~N}, \mathrm{Fe}_{3} \mathrm{H}, \mathrm{VH}_{0.58}$ and $\mathrm{TiH}_{1.7}$ etc. The important physical and chemical characteristics of these compounds are :
$(i)$ High melting points and even higher than pure metals.
$(ii)$ They are extremely hard. Some borides approach diamond in hardness.
$(iii)$ They retain metallic conductivity.
$(iv)$ They are chemically inert.
Percentage of silver in German silver is
In which pair of ions both are diamagnetic in nature?
The oxoanion in which the oxidation state of the central atom is same as its group number in the periodic table is
The correct order of the first ionization enthalpies is
Explain trends in $M^{2+}/M$ standard electrode potentials.