isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons, giving them different atomic masses but identical chemical properties.

• isotopic/ˌaɪsəˈtɒpɪk/(adj)同位素的

• radioactive isotope
• stable isotope
• carbon isotope
• isotope dating
• isotopic analysis

1. 1.Carbon-14, a radioactive isotope of carbon, decays at a known rate — allowing archaeologists to date organic materials up to 50,000 years old. (atoms with different neutron counts)
2. 2.Doctors use radioactive isotopes of iodine to both diagnose and treat thyroid conditions, because the thyroid naturally absorbs iodine. (medical application)

• nuclide/ˈnjuːklaɪd/— any atomic species defined by proton and neutron count — broader term

from Greek "isos" (equal) + "topos" (place) — same place in the periodic table, because isotopes occupy the same position