Valence or Valency Posted on 26th December 20153rd May 2021 by ThePD (The Project Definition) Valence or Valency is the numerical value of the charge on an ion that is to fill the outermost electron shell. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Science and tagged chemistry, physics, science. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.