Which statement correctly distinguishes isotope status from radioactivity?
Only radioactive atoms count as isotopes.
Every isotope is radioactive.
Some isotopes are stable and others are radioactive.✓Правильный ответ
Radioactivity depends only on electron count.
Объяснение
Isotopes vary in nuclear stability, so some are stable while others undergo radioactive change. Saying that every isotope is radioactive wrongly treats the word isotope as a synonym for radioactive isotope.