Which of the following specific pairs of transition elements are considered 'chemical twins' exhibit — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The poor shielding of the fourteen $4f$ electrons causes the 5d elements to shrink down to the exact size of their 4d counterparts. Consequently, Zirconium (1.45 Å) and Hafnium (1.44 Å) have identical radii and indistinguishable chemical properties.