What is IUPAC name of following compound?

Which element from following is the last element of 5d-transition series?

The solubility of $\mathrm{CaCO}_3$ is $7 \times 10^{-5} \mathrm{~mol} \mathrm{dm}^{-3}$ at $25^{\circ} \mathrm{C}$. What is its solubility product at same temperature?

Which of the following compounds is NOT obtained at any stage of Gabriel phthalimide synthesis?