Question

1. what is the electron configuration of a mn atom in the ground state?

1s²2s²2p⁶3s²3p⁶3d⁷
1s²2s²2p⁶3s²3p⁶4s¹3d⁴4p¹
1s²2s²2p⁶3s²3p⁶4s²3d⁵
1s²2s²2p⁶3s²
clear all

Explanation:

Manganese (Mn) has an atomic number of 25. The electron - filling order is based on the Aufbau principle. The 4s orbital is filled before the 3d orbital.

• For the first option \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{7}\), it does not account for the 4s electrons.
• For the second option \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{4}4p^{1}\), the electron - filling is incorrect as 4s should be filled before 3d and there is no reason for the 4p electron in the ground state.
• For the fourth option \(1s^{2}2s^{2}2p^{6}3s^{2}\), it only accounts for 12 electrons, far less than the 25 electrons of Mn.
• For the third option \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{5}\), \(2 + 2+6 + 2+6 + 2+5=25\). The 4s orbital is filled with 2 electrons before the 3d orbital (which has 5 electrons in the ground - state of Mn).

Answer:

\(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{5}\) (corresponding to the option \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{5}\))