Give the ground state electron configuration for Se.
The Correct Answer and Explanation is:
The correct answer to question 9, which asks for the ground state electron configuration of selenium (Se), is:
C) [Ar]4s²3d¹⁰4p⁴
Explanation
Selenium (Se) is a non-metal element in Group 16 and Period 4 of the periodic table, with an atomic number of 34. This means selenium has 34 electrons in its neutral ground state.
To write its electron configuration, we follow the Aufbau principle, which states that electrons fill orbitals in order of increasing energy levels. We also follow Hund’s rule and the Pauli exclusion principle to properly fill and pair electrons in orbitals.
Here’s the step-by-step electron filling until we reach 34 electrons:
- 1s² → 2 electrons
- 2s² → 2 electrons
- 2p⁶ → 6 electrons
- 3s² → 2 electrons
- 3p⁶ → 6 electrons
- 4s² → 2 electrons
- 3d¹⁰ → 10 electrons
- 4p⁴ → 4 electrons
Total:
2 + 2 + 6 + 2 + 6 + 2 + 10 + 4 = 34 electrons
To simplify, we use the noble gas argon (Ar) to represent the electron configuration of the first 18 electrons:
[Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶
So the full configuration becomes:
[Ar] 4s² 3d¹⁰ 4p⁴
This matches option C.
Why the others are incorrect:
- A) ends too early (missing electrons)
- B) misplaces 3d and 4s order (4s fills before 3d)
- D) has only 2 electrons in 4p instead of 4, indicating atomic number 32 (which is Ge, not Se)
- E) is a repeat of D
Thus, C is the correct configuration for Se, accurately reflecting the energy filling order and total number o
f electrons.