Question

the atomic number of manganese (mn) is 25. whats the electron configuration f manganese? a) ne 4s² 3p⁵ b) ar 3d⁵ 4s² c) ar 3s⁵ 4p² d) ne 3d⁷ question 4 (5 points)

Explanation:

To determine the electron configuration of manganese (Mn, atomic number 25), we start by recalling the electron - filling order and the noble gas notation. The noble gas before Mn (with atomic number less than 25) is argon (Ar, atomic number 18). The electron configuration of Ar is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}$. After accounting for the 18 electrons of Ar, we have 25 - 18 = 7 more electrons to distribute. The electron - filling order for the remaining electrons follows the Aufbau principle. The 4s orbital fills before the 3d orbital. The 4s orbital can hold 2 electrons, and then the remaining 5 electrons go into the 3d orbital. So the electron configuration of Mn is $[Ar]3d^{5}4s^{2}$.

• Option A: $[Ne]4s^{2}3p^{5}$ is incorrect. Ne has an atomic number of 10, and the configuration after Ne would not match the electron distribution for Mn. Also, the orbital filling order and the number of electrons in each orbital are wrong.
• Option B: $[Ar]3d^{5}4s^{2}$ matches the correct electron configuration we derived.
• Option C: $[Ar]3s^{5}4p^{2}$ is incorrect. The 3s orbital can only hold a maximum of 2 electrons, and the filling order of orbitals is violated here.
• Option D: $[Ne]3d^{7}$ is incorrect. Ne has 10 electrons, and the configuration does not account for the correct number of electrons and the proper orbital filling for Mn.

Answer:

B) $[Ar]3d^{5}4s^{2}$