Answer
See explanation below.
Work Step by Step
a.the maximum number of unpaired electrons in a lanthanide ion is 7 because f-block contains 7 orbitals.
b.The maximum number of unpaired electrons corresponds to a half-filled f subshell.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.