# What are the similarities and differences between the lanthanides series and the actinide series?

Apr 11, 2018

Mainly, the actinides have bigger orbitals, but their $5 f$ orbitals are more radially compact compared to the $4 f$ orbitals of the lanthanides, so there are more so-called "Aufbau exceptions" among the actinides.

Other factors are listed below, like electronegativities and oxidation states.

Here it is in a table... $\text{L""n}$ $=$ $\text{lanthanide}$, $\text{An}$ $=$ $\text{actinide}$.

" "" "" "ul(" "" "" ""Electroneg."" ""Atomic Radius"" "" ""Oxid. States"" ""Exceptions")
$\text{L""n"color(white)(..........)"Lower"" "" "" "" ""Smaller"" "" "" "" ""+3 usually"" "" } 3$
$\text{An"color(white)(.........)"Variable"" "" "" ""Larger"" "" "" "" "color(white)(.)"+3 to +7"" "" "" } 6$

• The electronegativities of the lanthanides are lower than for the actinides, but also more consistent. The actinide electronegativities are quite diverse. This is a graph made from data in Tro:

• The atomic radii of the actinides is bigger simply due to a new quantum level as expected.

• The actinides also achieve more diverse oxidation states due to higher $d$ orbital participation. Thus, their oxidation states range from $+ 3$ to $+ 7$. The $+ 3$ oxidation state is somewhat common among them, but less so than among the lanthanides.

Lanthanides:

Actinides:

• Lastly, there are more electron configuration exceptions among the actinides, due to that higher $6 d$ participation.

The exceptions are $\text{La}$, $\text{Ce}$, and $\text{Gd}$ for the lanthanides, and $\text{Ac}$, $\text{Th}$, $\text{Pa}$, $\text{U}$, $\text{Np}$, and $\text{Cm}$ for the actinides. In red are the exceptions.

$\textcolor{w h i t e}{\left[\begin{matrix}\textcolor{red}{L a} & \left(\textcolor{red}{\left[X e\right] 6 {s}^{2} 5 {d}^{1}}\right) & \textcolor{b l a c k}{T b} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{9}}\right) \\ \textcolor{red}{C e} & \left(\textcolor{red}{\left[X e\right] 6 {s}^{2} 4 {f}^{1} 5 {d}^{1}}\right) & \textcolor{b l a c k}{D y} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{10}}\right) \\ \textcolor{b l a c k}{P r} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{3}}\right) & \textcolor{b l a c k}{H o} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{11}}\right) \\ \textcolor{b l a c k}{N d} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{4}}\right) & \textcolor{b l a c k}{E r} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{12}}\right) \\ \textcolor{b l a c k}{P m} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{5}}\right) & \textcolor{b l a c k}{T m} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{13}}\right) \\ \textcolor{b l a c k}{S m} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{6}}\right) & \textcolor{b l a c k}{Y b} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{14}}\right) \\ \textcolor{b l a c k}{E u} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{7}}\right) & \textcolor{b l a c k}{L u} & \left(\textcolor{b l a c k}{\left[X e\right] 6 {s}^{2} 4 {f}^{14} 5 {d}^{1}}\right) \\ \textcolor{red}{G d} & \left(\textcolor{red}{\left[X e\right] 6 {s}^{2} 4 {f}^{7} 5 {d}^{1}}\right) & \text{ & }\end{matrix}\right]}$

$\textcolor{w h i t e}{\left[\begin{matrix}\textcolor{red}{A c} & \left(\textcolor{red}{\left[R n\right] 7 {s}^{2} 6 {d}^{1}}\right) & \textcolor{b l a c k}{B k} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{9}}\right) \\ \textcolor{red}{T h} & \left(\textcolor{red}{\left[R n\right] 7 {s}^{2} 6 {d}^{2}}\right) & \textcolor{b l a c k}{C f} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{10}}\right) \\ \textcolor{red}{P a} & \left(\textcolor{red}{\left[R n\right] 7 {s}^{2} 5 {f}^{2} 6 {d}^{1}}\right) & \textcolor{b l a c k}{E s} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{11}}\right) \\ \textcolor{red}{U} & \left(\textcolor{red}{\left[R n\right] 7 {s}^{2} 5 {f}^{3} 6 {d}^{1}}\right) & \textcolor{b l a c k}{F m} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{12}}\right) \\ \textcolor{red}{N p} & \left(\textcolor{red}{\left[R n\right] 7 {s}^{2} 5 {f}^{4} 6 {d}^{1}}\right) & \textcolor{b l a c k}{M d} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{13}}\right) \\ \textcolor{b l a c k}{P u} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{6}}\right) & \textcolor{b l a c k}{N o} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{14}}\right) \\ \textcolor{b l a c k}{A m} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{7}}\right) & \textcolor{b l a c k}{L r} & \left(\textcolor{b l a c k}{\left[R n\right] 7 {s}^{2} 5 {f}^{14} 6 {d}^{1}}\right) \\ \textcolor{red}{C m} & \left(\textcolor{red}{\left[R n\right] 7 {s}^{2} 5 {f}^{7} 6 {d}^{1}}\right) & \text{ & }\end{matrix}\right]}$

I cover those in detail here.