1. Atomic Structure

Subatomic Particles


  • Protons are positively charged subatomic particles. The charge of a proton is 1e, which corresponds to approximately 1.602 × 10-19
  • The mass of a proton is approximately 1.672 × 10-24
  • Protons are over 1800 times heavier than electrons.
  • The total number of protons in the atoms of an element is always equal to the atomic number of the element.


  • The mass of a neutron is almost the same as that of a proton i.e. 1.674×10-24
  • Neutrons are electrically neutral particles and carry no charge.
  • Different isotopes of an element have the same number of protons but vary in the number of neutrons present in their respective nuclei.


  • The charge of an electron is -1e, which approximates to -1.602 × 10-19
  • The mass of an electron is approximately 9.1 × 10-31.
  • Due to the relatively negligible mass of electrons, they are ignored when calculating the mass of an atom.

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