Answer:
The metals Co, Cu and Ti all require Roman numerals in the names of their compounds.
The elements Co, Ni, and Hg are all transition elements.
The elements P, As, and Bi are in the same family on the periodic table.
Explanation:
Transition elements are those which changes their charges as they bond with other elements or forms a compound with other elements. They show transitional behavior when they bond. Some of the transition elements are :
Chromium, Titanium, cobalt, mercury, copper, iron, vanadium, zinc, Silver, etc.
The transition elements use roman numerals in their names of the compounds.
Therefore, Cobalt (Co), Copper (Cu) and Titanium (Ti) are the elements that require a Roman numeral in the names of their compounds.
The elements Phosphorus (P), Arsenic (As) and Bismuth (Bi), they all belong to the nitrogen family of Group 15 (Va).