(પરમાણ્વિય ક્રમાંક : $\mathrm{Xe}=54, \mathrm{Ce}=58, \mathrm{Eu}=63$ )
\(\mathrm{Eu}^{2+} \Rightarrow[\mathrm{Xe}] 4 \mathrm{f}^{7}\)
\(\mathrm{Ce}_{58} \Rightarrow[\mathrm{Xe}] 4 \mathrm{f}^{1} 5 \mathrm{d}^{1} 6 \mathrm{s}^{2}\)
\(\mathrm{Ce}^{3+} \Rightarrow[\mathrm{Xe}] 4 \mathrm{f}^{1}\)