Ionic Radius
Part of the Atomic Structure section of Coddy's Chemistry journey. Lesson 38 of 45.
A positive ion is smaller than its atom. When sodium loses its outer electron, the whole outer shell goes: Na⁺ has 2 shells, not 3.
Na and Na⁺: losing the outer electron removes a whole shell
A negative ion is larger than its atom. Cl⁻ keeps 17 protons but gains an electron, and the extra electron pushes the others apart.
Isoelectronic ions have the same number of electrons, like O²⁻, F⁻, Na⁺ and Mg²⁺ (10 each). More protons pull the same 10 electrons in harder: O²⁻ > F⁻ > Na⁺ > Mg²⁺.
Challenge
Four ions share the same 10 electrons, the arrangement of neon: the oxide ion, the fluoride ion, the sodium ion and the magnesium ion. Build all four.
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Atomic Structure
1Matter and Atoms
What Everything Is Made OfElements, Compounds, MixturesChemical SymbolsCounting Atoms in a FormulaRecap - Molecule Kit