To identify which notation represents an excited state, we need to look for electron configurations in which electrons are not in the lowest energy orbitals available, which typically follow the Aufbau principle.
Let's analyze each option:
a) 1s² 2s² 2p¹
- This configuration indicates that there are 5 electrons in total. The 1s and 2s orbitals are completely filled, but there is only 1 electron in the 2p orbital. This is likely the ground state for an atom with 5 electrons, which is boron (B).
b) 1s² 2s² 2p³ 3s¹
- This configuration has 8 electrons. The 1s, 2s, and 2p orbitals are all filled according to the Aufbau principle, and there is an extra electron in the 3s orbital, which is a higher energy level than the filled 2p orbital. This indicates that one of the electrons from the lower energy levels (most likely the 2p) has been promoted to a higher energy state (3s). This means this atom is in an excited state. The element is oxygen (O) in an excited state since it has 8 electrons.
c) 1s² 2s² 2p⁶ 3s² 3p¹
- This configuration has 13 electrons. The 1s, 2s, 2p, and 3s orbitals are all filled according to the Aufbau principle, and there is one electron in the 3p orbital. This is the ground state configuration for aluminum (Al) with 13 electrons.
Conclusion: The notation that represents the electron configuration of a neutral atom in an excited state is b) 1s² 2s² 2p³ 3s¹ (oxygen in an excited state), because it indicates one of the 2p electrons has moved to a higher energy 3s orbital.
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