By Jack Brubaker
Updated Aug 30, 2022
The Bohr model—introduced by physicist Niels Bohr in 1913—offers a clear, visual way to introduce atomic structure. It depicts atoms as miniature solar systems, with electrons orbiting a dense nucleus. Although modern quantum mechanics provides a more nuanced picture, the Bohr model remains a valuable teaching tool, especially for early chemistry students.
A neutral helium atom (the simplest noble gas) contains two protons, two neutrons, and two electrons. The following guide shows how to sketch this atom using the Bohr framework.
Draw a circle about 2 inches (5 cm) in diameter. This will represent the nucleus.
Inside the nucleus, add two "+" symbols to denote the two positively charged protons.
Next, place two small “0” symbols within the same circle to indicate the two uncharged neutrons.
Enclose the nucleus with a larger circle, leaving roughly a half‑inch (1.3 cm) gap between the two circles. This outer ring represents the electron orbit. Mark two small “e” symbols on the orbit to show the two electrons circling the nucleus.
In a neutral atom such as helium, the number of electrons always equals the number of protons.
