Isotopes: Atoms of an element with the same atomic number but different mass numbers

Similarities:
a) Same number of protons
b) Same number of electrons
c) Same atomic number

Differences:
d) Different numbers of neutrons
e) Different mass numbers

Term "isotope" first used by Soddy
Greek origin: "isos" (same) + "tope" (place)
Contradicts Dalton'satomic theory of identical atoms for a given element

• Protium (H)
• Deuterium (D)
• Tritium (T)

Heavy water: Contains Deuterium instead of Protium

• Carbon-12
• Carbon-13
• Carbon-14

• Chlorine-35
• Chlorine-37

Natural abundance details

• Uranium-234
• Uranium-235
• Uranium-238

Natural abundance and applications
Fission of Uranium-235

Calculation method using isotopic masses and relative abundance
Example with carbon

• Medical applications (e.g., Iodine-131, Sodium-24, Cobalt-60)
• Scientific applications (e.g., Carbon-14 in photosynthesis research)
• Archaeological dating