Simple Model Of The Atom

Simple Model Of The Atom

  • Every atom has a central, positively charged nucleus that is very small but massive
  • The nucleus is made up of positive protons and neutral neutrons
  • Electrons revolve around the nucleus in allowed orbits
  • A vast amount of empty space within an atom


  • Mass: 9.1094 x 10-31 kg
  • Charge: -1.602 x 10-19 C

Nucleus diameter: around 10-15 m
Atomic diameter: around 10-10 m


  • Mass: 1836 x mass of electron, 1.6726 x 10-27kg
  • Charge +1.602 x 10-19 C


  • Mass: 1839 x mass of electron, 1.6749 x 10-27 kg
  • Charge: Neutral

Proton number (atomic number), Z, gives the number of protons in a nucleus.

The nucleon number (mass number), A, gives the total number of nucleons(protons + neutrons) in the nucleus.
A = Z + N, where N is number of neutrons in the nucleus.

Isotopes are atoms that have the same number of protons but different number of neutrons.

  • Same number of electrons
  • Same chemical properties


Back To Nuclear Physics (A Level)

Back To A Level Topic List

Sharing is caring:
Mini Physics

Administrator of Mini Physics. If you spot any errors or want to suggest improvements, please contact us.

Leave a Comment