Which ion has the same electron configuration as Kr

Which ion has the same electron configuration as Kr?

Rb+

Br-

Se2-

All of these?

The correct answer and explanation is:

Correct Answer: All of these

Explanation:

The electron configuration of a neutral krypton (Kr) atom is:

Kr: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶

This configuration totals 36 electrons. Any ion that also has 36 electrons will share this electron configuration.

Let us examine each ion one by one:

1. Rb⁺ (Rubidium ion)
   A neutral rubidium (Rb) atom has 37 electrons. When it loses one electron to form Rb⁺, it has 36 electrons remaining. Therefore, Rb⁺ has the same electron configuration as Kr.
2. Br⁻ (Bromide ion)
   A neutral bromine (Br) atom has 35 electrons. When it gains one electron to form Br⁻, it has 36 electrons. So, Br⁻ also shares the same electron configuration as Kr.
3. Se²⁻ (Selenide ion)
   A neutral selenium (Se) atom has 34 electrons. When it gains two electrons to become Se²⁻, it has 36 electrons. This means Se²⁻ also has the same configuration as Kr.

Each of these ions adjusts its electron count by either losing or gaining electrons to achieve the stable noble gas configuration of krypton. This process is a common behavior among elements in order to attain a full valence shell, which provides greater chemical stability.

Since Rb⁺, Br⁻, and Se²⁻ each end up with 36 electrons, and krypton also has 36 electrons, they all have the same electron configuration.

Conclusion: The correct answer is All of these because each of the ions achieves the same total number of electrons as krypton, resulting in identical electron configurations.