Answer:
2) The outer electron of atom B has moved to a lower energy state.
Explanation:
Properly writing the sublevel notations:
Atom A = 1s² 2s² 2p⁶ 3s¹
Atom B = 1s² 2s² 2p⁶ 5s¹
Solution:
According to the Aufbau's principle, "the sublevels with the lower energies are filled up before those with higher energies".
The pattern of filling is shown below:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5d, 6s, 4f, 5d, 6p, 7s, 5f, etc.
The configuration of atom A having a total of 11 electrons follows the Aufbau's rule as we can see.
For atom B, we see a higher energy level which is the 5s coming into the lower energy orbitals. Therefore, the outer electrons of atom B has moved to a lower energy state.
