What has the lowest mass of any charged leptop ?
Quantum rule The angular momentum is an integer multiple of " ħ " : : formula_8 Substituting the expression for the velocity gives an equation for " r " in terms of n : : formula_9 so that the allowed orbit radius at any n is : : formula_10 The smallest possible value of " r " in the hydrogen atom is called the Bohr radius and is equal to : : formula_11 The energy of the " n " - th level for any atom is determined by the radius and quantum number : : formula_12 An electron in the lowest energy level of hydrogen ( ) therefore has about 13.6 eV less energy than a motionless electron infinitely far from the nucleus .