Question

According to Aufbau principle, the increasing order of energies of 3d, 4s, and 4p orbitals is:

• A. 4p < 3d < 4s
• B. 4s < 4p < 3d
• C. 4s < 3d < 4p
• D. 3d < 4s < 4p

Answer 1

The correct option is C 4s < 3d < 4p

According to Aufbau principle, the electrons occupy the atomic orbitals with the lower energy before filling those with higher energy.

The order of energy levels can be determined by (n + l) rule. Lower the (n +l) value, lower is the energy.

If two orbitals have equal (n+l) values, then the orbital with the lower n value will have lower energy.