The 5d transition series exhibits a massive 14-element gap in atomic numbers immediately following w — d and f Block Elements Chemistry Question

💡 Solution & Explanation

In the 6th period, after Lanthanum ($Z=57$), the deeply buried $4f$ subshell begins to fill, creating a 14-element gap (the Lanthanoids) before the 5d series resumes with Hafnium ($Z=72$).