Which from following metal ions in their respective oxidation states forms coloured compound?

Calculate the density of an element having molar mass $63 \mathrm{~g} \mathrm{~mol}^{-1}$ that forms fcc structure $\left[\mathrm{a}^3 \times \mathrm{N}_{\mathrm{A}}=28 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right]$

Which from following groups is selected as principal functional group for nomenclature of a polyfunctional compound according to IUPAC system?

Identify the structure of $\mathrm{XeF}_4$ molecule from following.