* Barium (Ba) is in group 2 of the periodic table. This means it has 2 valence electrons.
* Barium loses these 2 electrons to form a +2 ion (Ba²⁺).
* The number of electrons in a neutral barium atom is 56. Losing 2 electrons leaves the ion with 54 electrons.
* The noble gas with 54 electrons is Xenon (Xe).
Therefore, the noble gas that has the same number of electrons as a barium ion is Xenon.
