Question

Select incorrect reaction of lanthanide (Ln):
A. ${{Ln}} + {{{H}}_2}{{O}}\xrightarrow{{{\Delta }}}{{Ln}}{\left( {{{OH}}} \right)_{{3}}} + {{{H}}_2} \uparrow$
B. ${{Ln}} + {{{N}}_2}\xrightarrow{{{\Delta }}}{{LnN}}$
C.${{Ln}} + {{{S}}_8} \to {{L}}{{{n}}_2}{{{S}}_3}$
D. ${{Ln}} + {{C}} \to {{L}}{{{n}}_4}{{C}}$

Answer 1

The elements with atomic numbers from 58 (cerium) to 71 (lutetium) are known as lanthanoids. Lanthanoids lie in the f-block of the periodic table. The valence electron of all the lanthanides lies in the 4f orbital.

Complete step by step answer:
Lanthanoids when treated with water form hydroxides and liberate hydrogen gas. The lanthanide hydroxides are basic and ionic in nature. The balanced chemical reaction is as follows:
${{Ln}} + 3{{{H}}_2}{{O}}\xrightarrow{{{\Delta }}}{{Ln}}{\left( {{{OH}}} \right)_{{3}}} + 3{{{H}}_2} \uparrow$
Thus, the reaction ${{Ln}} + {{{H}}_2}{{O}}\xrightarrow{{{\Delta }}}{{Ln}}{\left( {{{OH}}} \right)_{{3}}} + {{{H}}_2} \uparrow$ is correct.
Lanthanides on heating with nitrogen form lanthanide nitrides. The balanced chemical reaction is as follows:
${{2Ln}} + {{{N}}_2}\xrightarrow{{{\Delta }}}{{2LnN}}$
Thus, the reaction ${{Ln}} + {{{N}}_2}\xrightarrow{{{\Delta }}}{{LnN}}$ is correct.
Lanthanides on heating with sulphur form lanthanoid sulphides. The balanced chemical reaction is as follows:
${{16Ln}} + 3{{{S}}_8} \to 8{{L}}{{{n}}_2}{{{S}}_3}$
Thus, the reaction ${{Ln}} + {{{S}}_8} \to {{L}}{{{n}}_2}{{{S}}_3}$ is correct.
Lanthanides on reaction with carbon form lanthanide carbides having formula ${{L}}{{{n}}_{{3}}}{{C}}$, ${{Ln}}{{{C}}_{{2}}}$ and ${{L}}{{{n}}_2}{{{C}}_3}$. The reaction is as follows:
${{Ln}} + {{C}} \to {\text{Lanthanoid carbide}}$
${{L}}{{{n}}_4}{{C}}$ is not formed in the reaction.
Thus, the reaction ${{Ln}} + {{C}} \to {{L}}{{{n}}_4}{{C}}$ is not correct.

Thus, the correct option is option (D).

Note:
The general electronic configuration of lanthanoids is $4{f^{1 - 14}}\,5{d^{0 - 1}}\,6{s^2}$. Lanthanides belong to the group three of the periodic table. The common oxidation state exhibited by all the lanthanides is +3. Some of the lanthanoids show +2 and +4 oxidation state.
The atomic and ionic radii of the lanthanoids decrease gradually with an increase in atomic number. This is known as lanthanoid contraction.
The early members of the lanthanoid series are very reactive and are similar to calcium. As the atomic number increases, lanthanoids behave similar to aluminium. Lanthanoids form carbides, hydrides, oxides, nitrides, hydrides, hydroxides and sulphides.