Atomic radius is not a hard sphere
An atom has no sharp surface like a hard sphere. Atomic radii are quantities defined from measured distances or models.
Start with the idea
An atom has no sharp surface like a hard sphere. Atomic radii are quantities defined from measured distances or models.
A concrete example
Comparing radii only makes sense when the same definition and comparable conditions are used.
Mendeleev’s tip
Do not start with a formula. Identify what changes, what stays constant and which quantity you are trying to explain or calculate.
Go one step deeper
Covalent, metallic and van der Waals radii do not answer exactly the same question. Always check the definition before comparing.
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?