Can lanthanum ion exist in +4 oxidation state?Justify

No, Lanthanum can not exist in +4 oxidation states. This can be justify on the basis of electronic configuration of lanthanum.
Lanthanum: Atomic number =57 = 1s22s22p63s2​3p64s23d​104p64d105s25p65d16s2
Lanthanum can lose only 3 electrons, two from the s-subshell and one from the d-subshell to attain the noble gas configuration. So, it can not show the +4 oxidation state.
 

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