Final answer:
Chemical mutations can be caused by certain chemicals that interact with DNA, but X-rays belong to a different category known as ionizing radiation.
Step-by-step explanation:
Chemical mutations can occur when certain chemicals interact directly with DNA, either by acting as nucleoside analogs or by modifying nucleotide bases. Chemicals such as nitrogen mustard, hydroxylamine, ethyl methanesulfonate, and nitrous acid are all examples of chemical mutagens that can introduce mutations in DNA. However, X-rays are not considered a chemical mutation as they belong to the category of ionizing radiation, which can cause breaks in the DNA backbone or modify bases to alter their base-pairing rules.