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 Physics)

Back To A Level Physics Topic List

Mini Physics

As the Administrator of Mini Physics, I possess a BSc. (Hons) in Physics. I am committed to ensuring the accuracy and quality of the content on this site. If you encounter any inaccuracies or have suggestions for enhancements, I encourage you to contact us. Your support and feedback are invaluable to us. If you appreciate the resources available on this site, kindly consider recommending Mini Physics to your friends. Together, we can foster a community passionate about Physics and continuous learning.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.