Final answer:
The reaction NiCl₂ → Ni₂ + Cl₂ is a decomposition reaction, where a single compound breaks down into simpler substances.
Step-by-step explanation:
The type of chemical reaction represented by NiCl₂ → Ni + Cl₂ is a decomposition reaction. In this reaction, the compound nickel(II) chloride ('NiCl₂') decomposes into nickel metal ('Ni') and chlorine gas ('Cl₂'). A decomposition reaction is characterized by a single compound breaking down to form two or more simpler substances. This can be contrasted with other types of reactions such as synthesis, combustion, and single replacement reactions. Synthesis reactions involve the combination of elements or compounds to form a new substance, combustion reactions involve the burning of substances in oxygen, and single replacement reactions involve an element replacing another element in a compound.