Interstitial compounds are formed when small atoms fit into the interstices (spaces) of the metal lattice. They often involve transition metals and elements like hydrogen, boron, carbon, or nitrogen. Here’s a detailed explanation of why the statement "They are chemically reactive" is incorrect:
High Melting Points: Interstitial compounds typically have high melting points. The presence of small atoms in the metal lattice increases the melting point due to enhanced metallic bonding. This statement is correct.
Metallic Conductivity: These compounds maintain the metallic bonding and electron sea, allowing them to retain electrical conductivity. Thus, this statement is also correct.
Hardness: Interstitial compounds are known to be very hard. The interstitial atoms prevent the layers of metal atoms from sliding over each other easily, increasing hardness. This statement is correct.
Chemical Reactivity: Interstitial compounds are generally less chemically reactive compared to pure metals. The small interstitial atoms often stabilize the lattice and passivate the surface, reducing reactivity. Therefore, the statement "They are chemically reactive" is incorrect.
Thus, the incorrect statement among the given options regarding interstitial compounds is that they are chemically reactive. This directly contradicts their typical property of reduced chemical reactivity, which is primarily due to the stability and reduced surface activity provided by the interstitial atoms.
