The aufbau principle provides a helpful rule in the ordering of atomic orbitals.

The energy of the atomic orbital is decided by the size and shape of the orbital

Atomic orbitals are building blocks of the modern quantum mechanics model.

Spin quantum number decides the orientation of the intrinsic angular momentum.

Magnetic quantum number, m_l = … −2, −1, 0, 1, 2…

Azimuthal Quantum Number, l = 0, 1, 2, 3…

Principal Quantum Number, n = 1, 2, 3, 4…

Bohr's atomic theory was prosed by Neils Bohr in 1913. It was the first to inaugurate the quantum theory in the atom.