Question

Which of the following element(s) is/are not react directly with nitrogen to form nitride?
A.\[Na\]
B.\[Li\]
C.\[K\]
D.\[Rb\]

Answer 1

Hint: A nitride is a compound of nitrogen where nitrogen has a formal oxidation state of −3. The nitride ion, \[{N^{3 - }}\], is never encountered in a protic solution because it is so basic that it would be protonated immediately.
Anomalous behavior is a behavior that is different from its original order. It shows different properties from other members of its groups. Elements that show anomalous behavior have unique properties and form different compounds.

Complete answer:
Lithium shows anomalous behavior with respect to other alkali metal atoms. This is due to the following reasons:
1. Very small size of lithium atom and its ions.
2. Higher polarizing power of lithium results in increased covalent character of its compounds which is responsible for their solubility in organic solvents.
3. Comparatively high ionization enthalpy and low electropositive character of lithium as compared to other alkali metals.
4. Non availability of d-orbitals in its valence shell.
5. Strong inter metallic bonding.
When burnt in air or nitrogen, lithium forms Lithium nitride due to its high lattice energy because it shows anomalous behavior with respect to its other group (alkali metals) members. The Other alkali metals do not form their corresponding nitrides because their lattice energies decrease as their size increases from \[Na\] to \[Cs\].
\[6Li + {N_2} \to 2L{i_3}N\]
Hence, only \[Li\] reacts directly with nitrogen to form nitride. \[Na\],\[K\] and \[Rb\] do not react directly with nitrogen to form nitride.
Options (A), (C) and (D) are correct.

Note:
 Lithium nitride (\[L{i_3}N\]) is purple-reddish in color. Some oxides, nitrides can absorb hydrogen and have been discussed in the context of hydrogen storage, for example: lithium nitride.
 Sodium nitride has been generated, but remains a laboratory curiosity.