Question

Identify the pair of elements in which the number of electrons in the (n-1) shell is the same:

• A. Fe, Mn
• B. Zn, Fe
• C. K, Sc
• D. Mn, Cr

Hint:

Transition elements have their valence electrons in the \( (n) \) shell, while their \( (n-1) \) shell contains the d-electrons. When comparing elements, focus on the d-orbital occupancy to determine similarities in the \( (n-1) \) shell.

Answer 1

The Correct Option is D

In this problem, we need to identify the pair of elements that have the same number of electrons in the (n-1) shell, where n represents the principal quantum number.

We need to check the electron configurations of each pair of elements and compare the number of electrons in the (n-1) shell:

1. Fe and Mn:

Electron configuration of Fe: [Ar] 3d⁶ 4s²

Electron configuration of Mn: [Ar] 3d⁵ 4s²

The number of electrons in the (n-1) shell is different for both elements, so this is not the correct answer.

2. Zn and Fe:

Electron configuration of Zn: [Ar] 3d¹⁰ 4s²

Electron configuration of Fe: [Ar] 3d⁶ 4s²

The number of electrons in the (n-1) shell is different for both elements, so this is not the correct answer.

3. K and Sc:

Electron configuration of K: [Ne] 3s² 3p⁶ 4s¹

Electron configuration of Sc: [Ar] 3d¹ 4s²

The number of electrons in the (n-1) shell is different for both elements, so this is not the correct answer.

4. Mn and Cr:

Electron configuration of Mn: [Ar] 3d⁵ 4s²

Electron configuration of Cr: [Ar] 3d⁵ 4s¹

Both elements have the same number of electrons (5 electrons) in the (n-1) shell, so this is the correct answer.