A materials scientist is choosing between zirconium and hafnium for a corrosion-resistant alloy. The ground-state electron configurations of the neutral atoms are shown.

Atom	Atomic number, \(Z\)	Ground-state electron configuration
\(\text{Zr}\)	\(40\)	\([\text{Kr}]\,4d^2 5s^2\)
\(\text{Hf}\)	\(72\)	\([\text{Xe}]\,4f^{14} 5d^2 6s^2\)

Across the intervening lanthanides, the \(4f\) subshell becomes filled as \(Z\) increases. A student initially predicts that \(\text{Hf}\) has a substantially larger atomic radius because its outer electrons occupy the \(n=6\) shell rather than the \(n=5\) shell. After accounting for the relative penetration and shielding ability of electrons in \(s\), \(d\), and \(f\) subshells, which outcome for the atomic radii is most likely, and what accounts for it?