To an acidified dichromate solution, a pinch of Na2O2 is added and shaken. What is observed ? — d and f Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: Density generally increases across a period and down a group in the d-block. Step 2: The elements of the third transition series (5d) have very high densities due to Lanthanoid contraction causing a decrease in atomic size while atomic mass is high. Step 3: Osmium (Os) has the highest density (~22.59 g/cm³) among all elements, which is slightly higher than iridium and significantly higher than platinum and gold. Thus, option (a) is correct.