Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei, resulting in different atomic masses. While isotopes have different masses, they have the same atomic number because the atomic number is determined by the number of protons in the nucleus, which remains constant for a given element. Here are some examples of isotopes with different masses but the same atomic number:
Hydrogen:
- Hydrogen-1 (or protium): Atomic mass ≈ 1.0078 amu
- Deuterium (hydrogen-2): Atomic mass ≈ 2.0141 amu
- Tritium (hydrogen-3): Atomic mass ≈ 3.0160 amu
Carbon:
- Carbon-12: Atomic mass = 12.0000 amu (defined as the standard)
- Carbon-13: Atomic mass ≈ 13.0034 amu
- Carbon-14: Atomic mass ≈ 14.0032 amu
Oxygen:
- Oxygen-16: Atomic mass = 15.999 amu (approximately)
- Oxygen-17: Atomic mass ≈ 16.999 amu
- Oxygen-18: Atomic mass ≈ 17.999 amu
Uranium:
- Uranium-235: Atomic mass ≈ 235.0439 amu
- Uranium-238: Atomic mass ≈ 238.0508 amu
These examples demonstrate how isotopes of the same element can have different masses due to variations in the number of neutrons, while their atomic numbers (determined by the number of protons) remain the same.