# Reason for needing multiple radii for the same atom [duplicate]

Why do we need different types of atomic radii? Why can't there be just one radii for an atom?

• Determining the atomic radii is rather difficult because there is an uncertainty in the position of the outermost electron – we do not know exactly where the electron is. This phenomenon can be explained by the Heisenberg Uncertainty Principle. To get a precise measurement of the radius, but still not an entirely correct measurement, we determine the radius based on the distance between the nuclei of two bonded atoms. The radii of atoms are therefore determined by the bonds they form. An atom will have different radii depending on the bond it forms; so there is no fixed radius of an atom. Aug 31, 2020 at 8:20
• It isn't about the "looking like a book problem" that is an issue here.. What have you attempted to find the answer before asking here? Aug 31, 2020 at 8:22
• If a question is asked on Chemistry SE site, then, in contrary to sites like Quora, it is expected from the author to elaborate the topic of the question by doing at least basic own topic review, writing what he/she has found and understood, and what is the stumble stone. The quick questions without explicitly expressed particular effort are not very welcome, and may be closed. If you explicitly write down your own effort to answer your questions, then probability to get satisfying answers raises significantly. Aug 31, 2020 at 8:44
• I remember Dudley Herschbach's experiments in Harvard University with crossed molecular beams in a vacuum. If the two beams are made of sodium or potassium atoms for the first one, and of chlorine molecules for the second, the reaction with formation of $\ce{NaCl}$ or $\ce{KCl}$ happens even when the distance between the beams is as high as $45$ Å or $4.5$ nm. This is more than $10$ times the usual dimension of sodium atom or chlorine molecule. Ref.: D. R. Herschbach, Disc. Faraday Soc. 33, 149 (1962) Aug 31, 2020 at 8:54
• It also depends on the state of the electron(s). When excited, they get carried away, a bit. Aug 31, 2020 at 20:02