Question

$\large \orange {\underline {\underline {\tt ❥︎ \ Question :}}}$
☯︎ Define iso electronic set.
☞︎︎︎ Explain the concept.
☞︎︎︎ Explain in detail.
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Answer 1

Iso-electronic species :- Species (atom, molecules or ions) having same number of electrons are called iso - electronic species. ( or you can also say that iso - electronic species have same electronic configuration )

For example :-

1. H⁻ , Li⁺ and Be²⁺ have same number of electrons.

2. Ne and Mg²⁺ are also said to be iso- electronic species because they have same number of electrons.

3. CO and N₂ are also iso- electronic species. CO has total 14 electrons ( 6 electrons from carbon and 8 electrons from oxygen ). N₂ also has 14 electrons because each nitrogen atom has 7 electrons.

[ Note :- Now a days this concept is extended to consider the same valence shell electron also ]

Additional Information :-

Isotope : Atoms of same element having same atomic number but different mass number are called isotope.

Example :- ₁H¹ , ₁H² , ₁H³

Isobar : Atoms of different elements with same mass number but different atomic number.

Example :- ₁₈Ar⁴⁰ and ₁₉K⁴⁰

Iso-sters : Species having same number of atoms and same number of electrons.

Example :- N₂O and CO₂

Number of atoms in N₂O and CO₂ are 3 and number of electrons in both species are 22.

Iso- diaphers : Species having same difference in the number of neutrons and protons.

Example :- C and O

Answer 2

$\Large{\underline{\underline{\bf{\color{peru}Iso\:Electronic\:Species\:;-}}}}$

☆ Those having same number of electrons $\bf{(e^-)}$ but different nuclear charge forms iso-electronic series.

$\bf\red{Examples,}$

1) $\bf{O^{2-}\:,\:F^{-}\:,\:Mg^{2+}}$ have 10 electrons. Hence, they are iso-electronic species.

2) $\bf{K^{+}\:,\:Ca^{2+}\:,\:S^{2-}\:,\:Cl^-}$ have 18 electrons. Hence, they are iso-electronic species.

3) $\bf{Ne\:,\:F^{-}}$ have 10 electrons. Hence, they are iso-electronics.

4) $\bf{N^{3-}\:,\:Al^{3+}\:,\:Mg^{2+}}$ have 10 electrons. Hence, they are iso-electronics.

____________________

♕ Now we take one the above example and clarify it.

✒ We take second example.

$\boxed{\begin{array}{cccc}\bf Species & \bf Z & \bf e^- \\ \frac{\qquad \qquad \qquad \qquad}{} & \frac{\qquad \qquad \qquad \qquad}{} & \frac{\qquad \qquad \qquad \qquad\qquad}{} \\ \bf K^+ & \sf 19 & \sf 18 \\ \\ \bf Ca^{2+} & \sf 20 & \sf 18 \\ \\ \bf S^{2-} & \sf 16 & \sf 18 \\ \\ \bf Cl^- & \sf 17 & \sf 18 \end{array}}$

$\bf\blue{Where,}$

• Z denotes the total number of electrons are present in that element.

• $\bf{e^-}$ denotes the number of electrons are present after gain/loss of valency electrons.

$\Large{\underline{\underline{\bf{\color{cyan}CHARACTERISTICS\:;-}}}}$

1. For iso-electronic species the atomic radius increases with decrease in effective nuclear charge.