4species that are isoelectronic with the cesium ion, cs+

4 species that are isoelectronic with the Cesium ion, Cs⁺ are Xenon atom (Xe), Iodide ion (I⁻), Tellurium ion (Te²⁻), and Barium ion (Ba²⁺)

To determine species that are isoelectronic with Cesium ion, Cs⁺,

First, we will define what is meant by isoelectronic

Isoelectronic refers to two atoms, ions, or molecules that have the same electronic structure and the same number of valence electrons.

∴ Isoelectronic species can simply be defined as atoms or ions that have the same number of electrons.

For example, Na⁺ and F⁻ are said to be isoelectronic because they have the same electronic configuration and equal number of electrons.

(NOTE:  Na⁺ and F⁻ both have 10 electrons)

Now, to determine 4 species that are isoelectronic with cesium ion, Cs⁺

We will find other atoms or ions that have the same number of electron as Cs⁺.

Cesium atom (Cs) has 55 electrons

∴ Cesium ion (Cs⁺) will have 54 electrons (because it has lost one electron)

Other species that have 54 electrons are

1. Xenon atom (Xe)

2. Iodide ion (I⁻)

3. Tellurium ion (Te²⁻)

4. Barium ion (Ba²⁺)

Each of the species list above has 54 electrons

∴ They are isoelectronic to the Cesium ion, Cs⁺

Hence, 4 species that are isoelectronic with the Cesium ion, Cs⁺ are Xenon atom (Xe), Iodide ion (I⁻), Tellurium ion (Te²⁻), and Barium ion (Ba²⁺)

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Examples might include;

Te²⁻, I⁻, Xe, and Ba²⁺.

How many electrons in a Cs⁺ ion?

Cs is a group 1 metal. It contains 55 electrons when neutral. A Cs atom loses one electron to form a Cs⁺ ion. The Cs⁺ ion shall contain 54 electrons.

By the Aufbau principle, electrons in an ion or atom will arrange to minimize their energy. The configuration of the 54 electrons in Cs⁺ will be the same as that in any other stable ion or atom with the same number of electrons.

What ions or atoms contain 54 electrons?

The atomic number of Xenon is 54. A neutral xenon atom contains 54 electrons. An Xe atom will be isoelectronic with the Cs⁺ ion.

Metal atoms from one period below Xe lose all their valence electrons to become isoelectronic with Xe and hence Cs⁺. For example, Ba is in group 2. Its atom contains two valence electrons when neutral. The Ba atom loses both to form the Ba²⁺ ion. The Ba atom contains 56 electrons when neutral. Ba²⁺ will contain 54, the same as Cs⁺. As a result, Ba²⁺ is also isoelectronic with Cs⁺.

Non-metal atoms from the same period as Xe gain electrons to become isoelectronic with Xe. For example, the atomic number of Te is 52. A Te atom gains two electrons to form a Te²⁻ ion. Each Te²⁻ ion will contain 54 electrons, which is the same as the number of electrons in a Cs⁺ ion. Te²⁻ will be isoelectronic with Cs⁺.

Similarly, an iodine atom (atomic number 53) is one electron away from Cs⁺. It gains one electron to form the I⁻ ion. The I⁻ ion will be isoelectronic as Cs⁺.