Question

Transition elements form binary compounds with halogens. Which of the following elements will form MF3 type compounds?

1. Cr
2. Co
3. Cu
4. Ni​

Answer 1

Cobalt (Co) is the transition metal that forms MF3 type compounds by typically forming cobalt(III) fluoride (CoF3). Chromium (Cr) can also form CrF3, while copper (Cu) and nickel (Ni) do not commonly form MF3 compounds. The correct answer is option: 2. Co

Step-by-step explanation:

• Transition elements form binary compounds with halogens, known as halides. The nature of these halides can be either ionic or covalent, depending predominantly on the oxidation state of the metal. In general, lower oxidation states lead to more ionic character, while higher oxidation states tend to result in covalent bonding.
• For MF3 type compounds, we are looking for elements that can exhibit a +3 oxidation state and bond with fluorine to form trihalides.
• Among the options provided (Cr, Co, Cu, Ni), cobalt (Co) is the transition metal which commonly forms an MF3 type compound, as in cobalt(III) fluoride (CoF3). Chromium (Cr) can also form CrF3, although it has multiple oxidation states.
• Copper (Cu) and nickel (Ni) typically do not form MF3 compounds in their common oxidation states; copper usually forms cuprous (Cu+) or cupric (Cu2+) compounds, while nickel commonly forms Ni2+ compounds, such as nickel(II) fluoride (NiF₂).