Chemistry

Problem

The early lanthanide elements introduce occupation of the 4f subshell, yet their chemistry and periodic trends often resemble one another closely. Answer the following questions about cerium (Z = 58) and the neighboring lanthanides using principles of atomic structure. (a) Write the noble-gas abbreviated ground-state electron configuration for cerium. (b) Cerium commonly forms a

\text{Ce}^{4+}

ion. Write the complete electron configuration for this ion and identify which subshells lose electrons during ion formation. (c) For both

\text{Ce}^{3+}

and

\text{Ce}^{4+}

, discuss how effective nuclear charge experienced by a 4f electron differs, and explain the consequence for the relative sizes (ionic radii) of the two ions. (d) Across the series from lanthanum (Z = 57) to neodymium (Z = 60), atomic radii decrease only slightly even though additional protons are added to the nucleus. Using your understanding of 4f electron shielding, explain this so-called "lanthanide contraction."

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