Answer:
2p←6d
Explanation:
The energy ordering of atomic orbitals is based on the Aufbau principle and can be represented in the increasing order of energy as follows:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s ..............
During electronic transitions, energy is absorbed when an electron gets excited from a lower to a higher energy level whereas energy is released in the form of photons or light when electrons fall back from a higher to a lower level.
Hydrogen atom has only one electron in its valence shell. Based on the Aufbau energy ordering as show above, the energy difference between the 6d and 2p orbital is the highest. Therefore, photon associated with the 6d-2p transition will have the highest energy.