All the lanthanoid elements form stable compounds containing the +3 cation. Of the few other ionic forms known, Ce forms the stable + 4 series of ionic compounds and Eu the stable + 2 series. Account for these unusual ionic forms in terms of their electronic configurations.

All the lanthanoid elements form stable compounds containing the +3 ca

1.	All the lanthanoid elements form stable compounds containing the +3 cation. Of the few other ionic forms known, Ce forms the stable + 4 series of ionic compounds and Eu the stable + 2 series. Account for these unusual ionic forms in terms of their electronic configurations.
Answer» ides are metallic elements in the periodic table from “Lanthanum to lutetium”. Lanthanides are elements of f-block in which 4F electron shell are filled. The atomic numbers RUN from 51 to 71. All the Lanthanide elements contain the +3 cations and forms the stable compounds. The ELECTRONIC configuration of Cerium is and it is stable at +4 cation. can lose one 'f' electron to form with the fixed Xenon configuration. The Europium configuration is and it is stable at +2 cation. earn an electron for the formation of with the configuration and has the additional “stability of a partially-filled shell”.