If an electron can be in any orbit around the nucleus in Bohr's model, then what determines the typical atomic size?

Question

An electron can goto higher orbits in its excited state so what determines the typical atomic size of an atom

note that I am asking only from the viewpoint of Bohr's orbit.

Answer 1

You may use expectation

$$\langle r \rangle_{1s}=\int_0^{\infty} r|\psi_{1s}(r)|^2 4\pi r^2 \, dr=\frac{3a_0}{2}$$

which is three halves of the Bohr radius.

In general, for hydrogen-like atom in particular state (without screening):

$$\langle n\ell |r| n\ell \rangle= \frac{n^2 a_0}{Z} \left[ \frac{3}{2}-\frac{\ell(\ell+1)}{2n^2} \right]$$

Answer 2

First it depends on how many protons and neutrons are in the nucleus. Then it depends on how many other electrons are arranged below it in other shells. Then it depends on how many electrons are in the same shell. Beyond that it may depend on how the atoms are arranged and other things. Note that the energy levels from lowest to highest are set by these different arrangements.