Radioactivity

• The unit in which atomic and nuclear masses are measured is called atomic mass unit (amu).

• One amu is defined as 1/12^th of the mass of an atom of isotope.

              i.e., 1 amu = $1.66\times {10}^{-27} \mathrm{kg}$

• Atomic masses can be measured using a mass spectrometer.

• The different types of atoms of the same element which exhibit similar chemical properties, but have different masses are called isotopes.
• Isotopes are the atoms of an elements whose nuclei have the same number of protons, but have different number of neutrons.
• Isobars are the nuclei with the same mass number (A), but with different atomic numbers.
• Isotones are the atoms of different elements with the same atomic weight, but with different atomic numbers.

Nucleus

• The nu…