Which element has the electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d5?
Show the answer and explanation
Correct answer
A. Mn
Principle or equation
The electron configuration determines the atomic number by summing the superscripts. The element with that atomic number is identified from the periodic table.
Why this answer is correct
Sum the electrons: 2+2+6+2+6+2+5 = 25. The element with atomic number 25 is manganese (Mn). Note that Cr has a special configuration [Ar] 3d5 4s1, but the given configuration is the expected one for Mn.
Example
For configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d5, total electrons = 25, so the element is Mn.
This published item includes a stored explanation and passed the platform’s publication workflow. It is independent preparation material, not a claim of an official or recalled examination question.