Isotope
Atoms of same element differing in neutron number.
Isotopes are distinct nuclear species (nuclides) of the same chemical element, sharing the same atomic number (number of protons) and position in the periodic table but differing in mass number due to varying numbers of neutrons. They have virtually identical chemical properties but different atomic masses and physical properties.
- field
- Nuclear physics, chemistry
- key_concept
- Atoms of same element with different neutron numbers
- popularized_by
- Frederick Soddy
- notable_examples
- Carbon-12, carbon-13, carbon-14
Lore & Background
Soddy recognized that emission of an alpha particle followed by two beta particles yielded an element chemically identical to the initial one but with a mass four units lighter and different radioactive properties. The term 'isotope' was suggested to Soddy by Margaret Todd during a conversation in which he explained his ideas.
Reader's Guide
The concept of isotopes revolutionized understanding of atomic structure and chemical elements. It resolved the puzzle of why different radioactive species could occupy the same place in the periodic table, leading to the recognition that elements could have multiple forms differing only in neutron number. This insight was foundational for nuclear physics, radiochemistry, and later applications in nuclear technology and medicine. The distinction between isotopes and nuclides clarifies that while isotopes group atoms by chemical element, nuclides emphasize nuclear properties. Isotopes have practical importance: radioactive isotopes (radioisotopes) are used in medicine and industry, while stable isotopes help trace chemical and biological processes. The notation system (e.g., carbon-14 or ¹⁴C) standardizes identification. The discovery also explained variations in atomic weights of elements from different sources, as shown by T. W.
Did You Know?
- Carbon-12, carbon-13, and carbon-14 are isotopes of carbon with 6, 7, and 8 neutrons respectively.
- For three elements (tellurium, indium, rhenium) the most abundant natural isotope is actually a long-lived radioisotope.
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