Electronic Configurations Of Elements And The Periodic Table

To determine which pair of elements has the same number of electrons in the (n-1) shell, we need to analyze the electron configurations of the elements:

• Iron (Fe): [Ar] 3d⁶ 4s²
• Manganese (Mn): [Ar] 3d⁵ 4s²
• Zinc (Zn): [Ar] 3d¹⁰ 4s²
• Potassium (K): [Ar] 4s¹
• Scandium (Sc): [Ar] 3d¹ 4s²
• Chromium (Cr): [Ar] 3d⁵ 4s¹

The (n-1) shell for the elements given is the 3rd shell, which corresponds to the 3d subshell. Let's analyze these configurations to find pairs with the same number of electrons in this shell:

• Fe (Iron): 3d⁶
• Mn (Manganese): 3d⁵
• Zn (Zinc): 3d¹⁰
• K (Potassium): 3d⁰
• Sc (Scandium): 3d¹
• Cr (Chromium): 3d⁵

We find that both Manganese (Mn) and Chromium (Cr) have 5 electrons in the 3d subshell.

Thus, the correct pair with the same number of electrons in the (n-1) shell is Mn, Cr.