**Isoelectronic Species**

Isoelectronic species are atoms, ions, or molecules that have the same number of electrons. They may have different atomic numbers and different chemical properties, but they share the same electron configuration. Isoelectronic species can be positive ions, negative ions, or neutral molecules.

**Isoelectronic Species with Mg²⁺**

To find an isoelectronic species with Mg²⁺, we need to consider the electron configuration of Mg²⁺, which is 1s²2s²2p⁶. We can see that Mg²⁺ has lost two electrons compared to the neutral Mg atom (1s²2s²2p⁶3s²).

One isoelectronic species with Mg²⁺ is the neon atom (Ne). Neon has an electron configuration of 1s²2s²2p⁶, which is the same as the Mg²⁺ ion. Both have a total of 10 electrons.

Another isoelectronic species with Mg²⁺ is the fluorine ion (F⁻). Fluorine has an electron configuration of 1s²2s²2p⁵. By gaining one electron, it becomes isoelectronic with Mg²⁺, both having 10 electrons.

**Isoelectronic Species with Ar**

To find an isoelectronic species with Ar, we need to consider the electron configuration of Ar, which is 1s²2s²2p⁶3s²3p⁶. We can see that Ar has a total of 18 electrons.

One isoelectronic species with Ar is the potassium ion (K⁺). Potassium has an electron configuration of 1s²2s²2p⁶3s²3p⁶4s¹. By losing one electron, it becomes isoelectronic with Ar, both having 18 electrons.

Another isoelectronic species with Ar is the calcium ion (Ca²⁺). Calcium has an electron configuration of 1s²2s²2p⁶3s²3p⁶4s². By losing two electrons, it becomes isoelectronic with Ar, both having 18 electrons.

**Explanation**

Isoelectronic species share the same number of electrons, which means they have the same electron configuration. The number of electrons determines the chemical properties of an atom or ion. By comparing the electron configurations of different species, we can identify isoelectronic species.

In the case of Mg²⁺, it has lost two electrons compared to the neutral Mg atom. To find an isoelectronic species, we look for atoms or ions that have the same number of electrons as Mg²⁺, which is 10. The neon atom (Ne) and the fluorine ion (F⁻) both have 10 electrons and are therefore isoelectronic with Mg²⁺.

Similarly, for Ar, which has 18 electrons, we look for species that also have 18 electrons. The potassium ion (K⁺) and the calcium ion (Ca²⁺) both have 18 electrons and are therefore isoelectronic with Ar.

Overall, isoelectronic species have the same electron configuration, which means they have similar chemical properties despite having different atomic numbers.

The entities ( atoms, molecules or ions) containing same number of electrons are said to be isoectronic.
for mg2+=Al3+,Na+,Ne,O2-forAr=Ca2+,K+