$x^{2+}$ is isoelectronic with sulphur and has (Z + 2) neutrons (Z is atomic no. of $x^{2+}$). Hence, ionic mass of $x^{2+}$ is:

$x^{2+}$ is isoelectronic with sulphur and has (Z + 2) neutrons (Z is atomic no. of $x^{2+}$). Hence, ionic mass of $x^{2+}$ is: 38

Elements or ions that contain the same number of electrons, or an equal number, are said to be isoelectronic species. Even though isoelectronic species have the same amount of electrons, their physical and chemical characteristics vary. The isoelectronic ions $x^{2+}$ and s are two examples (both ions have 16 electrons).

Hence, option C is correct.