This study investigates the atomic-like properties of artificial atoms in vertical quantum dots by measuring Coulomb oscillations in dots with tunable electron numbers. At zero magnetic field, the energy required to add an electron to the dot shows a shell structure in a 2D harmonic potential. As the magnetic field increases, current peaks shift in pairs due to the filling of spin-degenerate states. However, at small magnetic fields, Hund's rule predicts that parallel spin filling is favored. The addition energy, analogous to electron affinity in atoms, is found to be unusually large for specific electron numbers (magic numbers) such as 2, 6, and 12. These numbers correspond to complete shell filling in a 2D harmonic potential. The study also shows that the pairing of current peaks depends on the magnetic field, with even and odd N showing different behaviors. The electronic states in a magnetic field are analyzed using a 2D radial harmonic potential, revealing that the energy levels depend on the magnetic field. The calculated single-particle energy shows that the addition energy for even N is strongly dependent on the magnetic field, while for odd N, it is determined by Coulomb repulsion. The study also demonstrates that Hund's rule governs the spin filling in the second shell near zero magnetic field, with the electrochemical potential showing a specific dependence on the magnetic field. The results are consistent with the predicted shell structure and Hund's rule, and the study provides insights into the electronic properties of quantum dots.This study investigates the atomic-like properties of artificial atoms in vertical quantum dots by measuring Coulomb oscillations in dots with tunable electron numbers. At zero magnetic field, the energy required to add an electron to the dot shows a shell structure in a 2D harmonic potential. As the magnetic field increases, current peaks shift in pairs due to the filling of spin-degenerate states. However, at small magnetic fields, Hund's rule predicts that parallel spin filling is favored. The addition energy, analogous to electron affinity in atoms, is found to be unusually large for specific electron numbers (magic numbers) such as 2, 6, and 12. These numbers correspond to complete shell filling in a 2D harmonic potential. The study also shows that the pairing of current peaks depends on the magnetic field, with even and odd N showing different behaviors. The electronic states in a magnetic field are analyzed using a 2D radial harmonic potential, revealing that the energy levels depend on the magnetic field. The calculated single-particle energy shows that the addition energy for even N is strongly dependent on the magnetic field, while for odd N, it is determined by Coulomb repulsion. The study also demonstrates that Hund's rule governs the spin filling in the second shell near zero magnetic field, with the electrochemical potential showing a specific dependence on the magnetic field. The results are consistent with the predicted shell structure and Hund's rule, and the study provides insights into the electronic properties of quantum dots.