Complete the atomic orbital diagram for the ground-state electronic configuration of chlorine. Energy 1s 2s 2p 3s 3p 11 11 11 11 11 11 11 11 Answer Bank 1 11
The Correct Answer and Explanation is:
Correct Answer: The empty box in the 3p orbital should be filled with the single electron [↑] from the Answer Bank.
The completed atomic orbital diagram for chlorine is:
Energy
3p [↑↓] [↑↓] [↑]
3s [↑↓]
2p [↑↓] [↑↓] [↑↓]
2s [↑↓]
1s [↑↓]
Explanation
To complete the atomic orbital diagram for the ground state electronic configuration of chlorine, we must first determine the number of electrons in a neutral chlorine atom. Chlorine (Cl) has an atomic number of 17, which means it has 17 protons and 17 electrons. We will fill the atomic orbitals with these 17 electrons according to a set of established rules that define the lowest energy arrangement, known as the ground state.
The primary rules for electron filling are:
- The Aufbau Principle: Electrons fill the lowest energy orbitals first. The order of increasing energy is 1s, 2s, 2p, 3s, 3p, and so on.
- The Pauli Exclusion Principle: An orbital can hold a maximum of two electrons, and they must have opposite spins (represented as an up arrow and a down arrow).
- Hund’s Rule: When filling a subshell with multiple orbitals of the same energy (like the three 2p or three 3p orbitals), electrons are placed one at a time into each orbital with parallel spins before any orbital is doubly occupied.
Following these principles for chlorine’s 17 electrons:
- The first 2 electrons fill the 1s orbital (1s²).
- The next 2 electrons fill the 2s orbital (2s²).
- The next 6 electrons fill the three 2p orbitals (2p⁶).
- The next 2 electrons fill the 3s orbital (3s²).
At this point, we have placed a total of 2 + 2 + 6 + 2 = 12 electrons. The remaining 17 – 12 = 5 electrons must go into the 3p subshell.
According to Hund’s rule, we place the 5 electrons into the three 3p orbitals by first adding one electron to each orbital ([↑] [↑] [↑]), and then using the remaining two electrons to pair up with the electrons in the first two orbitals. This results in the configuration [↑↓] [↑↓] [↑].
The provided diagram correctly shows the first 12 electrons filling the 1s, 2s, 2p, and 3s orbitals. In the 3p subshell, two of the orbitals are shown with paired electrons, accounting for 4 of the 5 electrons needed. To complete the diagram for chlorine, the final, seventeenth electron must be placed in the last empty 3p orbital. Therefore, the correct choice from the Answer Bank is the single electron [↑]. This completes the ground state configuration for chlorine as 1s²2s²2p⁶3s²3p⁵.
