Final answer:
Argon cannot be decomposed by chemical change because it is a pure element, unlike sulfuric acid, ammonia, and water which are compounds.
Step-by-step explanation:
Argon, with the atomic number 18, belongs to the noble gas group on the periodic table, characterized by its stable and inert nature. Unlike compounds such as sulfuric acid, ammonia, and water, which consist of multiple elements chemically bonded together, argon exists as individual atoms. The key distinction lies in the fact that chemical processes cannot break down argon into simpler substances. Its stable atomic structure renders it immune to chemical decomposition, reinforcing its status as an elemental, pure substance. This inherent stability and indivisibility make argon an excellent example of an element that remains unchanged by chemical reactions, a fundamental concept in understanding the nature of matter.