Discuss the physical properties of lanthanoids. Discuss the trends in the ionization enthalpies of lanthanoids.

(N/A) All lanthanoids are silvery-white soft metals and tarnish rapidly in air.
The hardness increases with an increase in atomic number. Samarium is steel-hard.
The melting points range between $1000 \ K$ and $1200 \ K$. However,samarium melts at $1623 \ K$.
They show luster and are good conductors of heat and electricity.
Density and other properties change smoothly except for $Eu$ and $Yb$,and occasionally for $Sm$ and $Tm$. Lanthanoids are paramagnetic,except for ions like $La^{3+}$,$Ce^{4+}$,$Yb^{2+}$,and $Lu^{3+}$.
The first ionization enthalpies of the lanthanoids are around $600 \ kJ \ mol^{-1}$ and the second is about $1200 \ kJ \ mol^{-1}$,which are comparable to those of calcium.
The third ionization enthalpies of elements lanthanum $(La)$,gadolinium $(Gd)$,and lutetium $(Lu)$ are found to be exceptionally low because of the stability of $f^{0}$,$f^{7}$,and $f^{14}$ shells,respectively,in these elements.