To relate angular momentum to Equation 26-18, we express \(L\) in terms of the mass of the electron \(m_{\mathrm{e}}\), its speed \(v\), and its distance from the center of the atom \(r\) using Equation 8-23:
Since the electron moves in a circle, the vector from the rotation axis to the particle always has the same radius \(r\) and is always perpendicular to the momentum vector.