where 
is the permittivity of free space, 
is the mass of the electron, 
the charge on the proton, and 
is Planck's constant. [P8.2]
in: the Bohr model of the hydrogen atom
is: the radius of the smallest Bohr orbit for the electron. [P8.2, P11.3]
is given: by where is the permittivity of free space, is the mass of the electron, the charge on the proton, and is Planck's constant. [P8.2]
therefore is: quantized by Bohr's quantum number 
[P8.2]
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