M5S12 – Transition Elements

Which first-row d-block element has the electron configuration

1s²2s²2p⁶3s²3p⁶4s¹3d⁵?

Which of the first-row d-block metals forms aqueous ions which are mauve in the +2 state, green in the +3 state, blue in the +4 state and yellow in the +5 state?

Which first-row d-block metal forms aqueous ions in the +6 state which are orange in acid solution but yellow in alkaline solution?

Which first-row d-block metal has the main oxidation state +2 and forms colourless compounds?

Which first-row d-block metal forms aqueous ions in the +3 state which oxidise iodide ions to iodine?

Which first-row d-block metal forms a reddish oxide in the +1 state which dissolves in dilute sulfuric acid to give a blue solution and a red-brown precipitate?

Which metal forms aqueous ions in the +2 state which precipitate as a hydroxide on adding ammonia solution and redissolve to form a deep blue solution

Which first-row d-block metal forms hydrated ions in the +3 state which undergo a ligand exchange reaction to form a deep red complex ion with thiocyanate ions, SCN^-.

Which first-row d-block element forms an oxide used as the catalyst in the synthesis of sulfur trioxide from sulfur dioxide and oxygen?

Which first-row d-block element is used as the catalyst for the addition of hydrogen gas to C=C double bonds?