Question

What is isoelectronic?

Answer 1

Hint: The concept's significance lies in distinguishing closely related species as pairs or series. Since properties of isoelectronic species are supposed to be consistent and predictable, defining a compound as isoelectronic with one that has already been characterised provides clues to potential properties and reactions.

Complete answer:
Atoms or ions with the same number of electrons are known as isoelectronic entities. The number of electrons in isoelectronic species would be the same, but the elements would be different. In other words, isoelectronic species refers to ions and atoms that have the same number of electrons.

Isoelectronicity is a phenomenon that occurs when two or more molecules possess the same structure (positions and connectivities among atoms) and same electron configurations, but vary in which specific elements are present at certain points in the structure.
Examples: The isoelectronic pair $N{a^ + }$ and ${F^ - }$ has the electronic configuration $1{s^2}2{s^2}2{p^6}$.

Since, we know that the atomic number of fluorine is $9$. So, the total number of electrons in its ground state will be $9$. But there is one negative charge on fluorine, it means that it has one more electron in its shell. Hence, the fluorine ion has ten electrons ($9 + 1 = 10$). As a result, the isoelectronic species with ${F^ - }$ must also have $10$ electrons.

Now, we know this also that the atomic number of sodium is $11$. So, the total number of electrons in its ground state will be $11$. But there is one positive charge on sodium, it means that it released one electron from its outer shell. Hence, the sodium ion has ten electrons $(11 - 1 = 10)$. As a result, the isoelectronic species with $N{a^ + }$must have $10$ electrons.

Now, we can observe that ${F^ - }$ and $N{a^ + }$ have the same number of electrons, hence they both are isoelectronic species.
$CO$,${N_2}$and $N{O^ + }$ are also isoelectronic species.

Note: Isoelectronicity can be used to forecast a species' properties and reactions. It's used to distinguish between hydrogen-like atoms with one valence electron and thus are isoelectronic to hydrogen. Based on their electronic similarity to recognised organisms, the term can be used to predict or classify unknown or unusual compounds.