Answer
$O^{+}$ and $N$.
$Ar$ and $S^{2-}$.
$Ne$ and $N^{3-}$
$Zn$ and $As^{3+}$.
$Xe$ and $ Cs^{+}$
Work Step by Step
Atoms or ions with the same number of electrons are called iso-electronic species.
$O^{+}$ and $N$.
The atomic number of Oxygen = 8.
$O^{+}$ is formed by the removal of one electron from an Oxygen atom.
Therefore number of electrons in $O^{+}$ = 7.
The atomic number of Nitrogen = 7.
Therefore number of electrons in $N$ = 7.
$Ar$ and $S^{2-}$.
The atomic number of Argon = 18.
Therefore number of electrons in $Ar$ = 18.
The atomic number of Sulphur = 16.
$S^{2-}$ is formed by the addition of two electrons to the Sulphur atom.
Therefore number of electrons in $S^{2-}$ = 18.
$Ne$ and $N^{3-}$
The atomic number of Neon = 10.
Therefore number of electrons in $Ne$ = 10.
The atomic number of Nitrogen = 7.
$N^{3-}$ is formed by the addition of three electrons to a Nitrogen atom.
Therefore number of electrons in $N^{3-}$ = 10.
$Zn$ and $As^{3+}$.
The atomic number of Zinc = 30.
Therefore number of electrons in $Zn$ = 30.
The atomic number of Arsenic = 33.
$As^{3+}$ is formed by the removal of three electrons from an Arsenic atom.
Therefore number of electrons in $As^{3+}$ = 30.
$Xe$ and $ Cs^{+}$
The atomic number of Xenon = 54.
Therefore the number of electrons in $Xe$ = 54.
The atomic number of Caesium = 55.
$Cs^{+}$ is formed by the removal of one electron from a Caesium atom.
Therefore number of electrons in $Cs^{+}$ = 54.
