What is the electron configuration for Zn? A) 1s22s22p63s23p63d104s24p6 B) 1s22s22p63s23p64s23d104p1 C) 1s22s22p63s23p53d104s24p1 D) 1s22s22p63s23p64s24d104p1 E) 1s22s22p63s23p64s23d10
The Correct Answer and Explanation is:
The correct answer is:
E) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰
Explanation:
Zinc (Zn) has an atomic number of 30, which means it has 30 electrons. To write the electron configuration, we fill the atomic orbitals following the Aufbau principle, Pauli exclusion principle, and Hund’s rule. The order of orbital filling is based on increasing energy levels, not just the principal quantum number.
Here is the step-by-step filling:
- 1s² → 2 electrons
- 2s² → 2 electrons
- 2p⁶ → 6 electrons
- 3s² → 2 electrons
- 3p⁶ → 6 electrons
- 4s² → 2 electrons (filled before 3d because 4s is lower in energy at first)
- 3d¹⁰ → 10 electrons (fully fills the d-subshell)
Adding all those gives:
2 (1s) + 2 (2s) + 6 (2p) + 2 (3s) + 6 (3p) + 2 (4s) + 10 (3d) = 30 electrons
This configuration ends in 4s² 3d¹⁰, which is the correct full electron configuration for zinc.
Why the other options are incorrect:
- A) ends with 4p⁶ which is beyond atomic number 30
- B) ends with 4p¹, suggesting atomic number 31 (gallium)
- C) has 3p⁵, which is incorrect for Zn
- D) lists 4d¹⁰, but 4d orbitals are filled later, around atomic number 39 (yttrium)
So, option E is correct because it properly accounts for all 30 electrons and ends with a full 3d subshell after the 4s orbital is filled.
