Discuss the chemical properties of lanthanoids.

(N/A) The earlier members of the series show chemical behavior similar to that of calcium. However,with an increase in atomic number,they behave more like aluminium.
The $E^{\circ}$ values for the half-reaction $Ln_{(aq)}^{3+} + 3e^{-} \rightarrow Ln_{(s)}$ range from $-2.2 \ V$ to $-2.4 \ V$,except for $Eu$,which has a value of $-2.0 \ V$.
Lanthanoids react with hydrogen when heated gently in the gas. When heated with carbon,they form carbides of the types $Ln_{3}C$,$Ln_{2}C_{3}$,and $LnC_{2}$.
These metals form trihalides $(LnX_{3})$ with halogens and liberate hydrogen gas when treated with dilute acids. They combine with oxygen to form oxides of the type $Ln_{2}O_{3}$. These oxides are basic in nature and react with water to form hydroxides,$Ln(OH)_{3}$. The basicity of these oxides and hydroxides is intermediate between that of aluminium and calcium compounds:
$Al_{2}O_{3} < Ln_{2}O_{3} < CaO$
$Al(OH)_{3} < Ln(OH)_{3} < Ca(OH)_{2}$
As the atomic number increases,the basicity of the hydroxides decreases due to lanthanoid contraction.
Summary of chemical reactions:
- With $O_{2}$: Forms $Ln_{2}O_{3}$
- With acids: Liberates $H_{2}$
- With halogens: Forms $LnX_{3}$
- With $H_{2}O$: Forms $Ln(OH)_{3} + H_{2}$
- With $C$ (at $2773 \ K$): Forms $LnC_{2}$
- With $N$: Forms $LnN$
- With $S$: Forms $Ln_{2}S_{3}$