What's the difference between an X-ray and a bone scan?

Both radiation. Nuclear medicine radiation is given internally via IV injection, ingestion, or inhalation for determination of function of organs of body. Isotopes have different half lives and decay at different rates.Ct/xray is external radiation for visualization of anatiomy and pathology. Both contribute to radiation dose. Both are ionizing radiation. Ultrasound and MRI do not involve irradiation.
Emission / transmiss. A bone scan images bone physiology... How the bone is metabolizing calcium. An x-ray looks at the anatomy of the bone. A bone scan is an emission scan and x-ray a transmission scan. A bone scan is a nuclear medicine procedure, and an x-ray a radiology procedure.