By Mariecor Agravante
Updated Mar 24, 2022
Sodium (Na) is a soft, silvery‑white alkali metal that makes up roughly 2.8 % of the Earth’s crust. Crafting a three‑dimensional representation of its atom offers a tangible way to explore atomic structure and the classic Bohr model.
The Bohr model, introduced by Danish physicist Niels Bohr, visualizes the atom as a miniature solar system: a central nucleus (protons and neutrons) surrounded by electron shells that hold electrons in stable orbits. Though modern quantum mechanics has refined this picture, the Bohr framework remains a valuable teaching tool for understanding electron configuration and shell capacity.
Use two cotton‑ball sizes: larger ones for protons and neutrons, smaller ones for electrons. Build concentric cardboard rings to represent electron shells.
Select cotton balls that differ in size to mirror the relative sizes of protons/neutrons versus electrons. Cut cardboard into rings that will become the electron shells; use string to tie the rings into concentric circles. Glue the cotton balls onto the appropriate regions.
Sodium’s atomic number is 11, meaning it has 11 protons and, in a neutral atom, 11 electrons. Use 11 yellow cotton balls to represent protons. The nucleus also contains neutrons; the atomic weight of sodium is about 23, so 23 – 11 = 12 neutrons. Use 12 green cotton balls for neutrons.
As noted, sodium’s nucleus contains 12 neutrons. The 11 yellow protons and 12 green neutrons together form the nucleus that sits at the center of your model.
The Bohr model describes electron shells as principal energy levels with capacity limits: the nth shell can hold up to 2n² electrons. Thus:
Position the nucleus at the center, then layer the electron shells outward. Tie the shells together with string to keep the model stable. The finished structure offers a clear, hands‑on illustration of sodium’s atomic architecture.
