Mendeleev · science lesson
Ionic radius: why charge matters
Losing or gaining electrons changes electron repulsion and effective nuclear attraction, often changing ion size strongly.
Start with the idea
Losing or gaining electrons changes electron repulsion and effective nuclear attraction, often changing ion size strongly.
A concrete example
Na⁺ is smaller than Na in common models, while Cl⁻ is larger than Cl.
Practical method
Go one step deeper
Within an isoelectronic series, more protons attract the same number of electrons more strongly, so radius tends to decrease.
Common trap
A trend or model is not an exceptionless law. Always check the quantity’s definition and the conditions being compared.
Check your understanding
Can you explain the phenomenon in your own words before looking at an equation?