select the correct electron configurations from the list below

select the correct electron configurations from the list below. You can refer to the periodic table for atomic numbers.

The electron configuration of Cu+ is [Ar]4s13d9.

The electron configuration of S2− is [Ne]3s23p6.

The electron configuration of Fe is [Ar]4s23d6.

The electron configuration of Si is [Ne]3s23p2.

The electron configuration of Rb is [Kr]5s04d1.

The correct answer and explanation is :

Let’s analyze each given electron configuration and determine its correctness.

1. Cu⁺ (Copper ion, +1 charge)

• Given: [Ar]4s¹3d⁹
• Correct Configuration: [Ar]3d¹⁰
• Explanation: Copper (Cu) has an atomic number of 29, with a neutral configuration of [Ar]4s¹3d¹⁰ (due to stability considerations). When Cu loses one electron to form Cu⁺, it loses the 4s electron first, resulting in [Ar]3d¹⁰. Thus, the given configuration is incorrect.

1. S²⁻ (Sulfide ion, -2 charge)

• Given: [Ne]3s²3p⁶
• Correct Configuration: [Ne]3s²3p⁶
• Explanation: Sulfur (S) has an atomic number of 16, with a neutral configuration of [Ne]3s²3p⁴. When it gains two electrons to form S²⁻, it achieves the noble gas configuration of argon, [Ne]3s²3p⁶. Thus, this configuration is correct.

1. Fe (Iron, neutral atom)

• Given: [Ar]4s²3d⁶
• Correct Configuration: [Ar]4s²3d⁶
• Explanation: Iron (Fe) has an atomic number of 26, with a neutral configuration of [Ar]4s²3d⁶. The given configuration is correct.

1. Si (Silicon, neutral atom)

• Given: [Ne]3s²3p²
• Correct Configuration: [Ne]3s²3p²
• Explanation: Silicon (Si) has an atomic number of 14, with a neutral configuration of [Ne]3s²3p². The given configuration is correct.

1. Rb (Rubidium, neutral atom)

• Given: [Kr]5s⁰4d¹
• Correct Configuration: [Kr]5s¹
• Explanation: Rubidium (Rb) has an atomic number of 37, with a neutral configuration of [Kr]5s¹. The given configuration is incorrect. The electron should be in the 5s orbital, not in the 4d orbital.

Final Evaluation:

✅ Correct Configurations:

• S²⁻: [Ne]3s²3p⁶
• Fe: [Ar]4s²3d⁶
• Si: [Ne]3s²3p²

❌ Incorrect Configurations:

• Cu⁺: Should be [Ar]3d¹⁰
• Rb: Should be [Kr]5s¹

This analysis follows the Aufbau principle, Hund’s rule, and the order of orbital filling.