Which of the following ions is isoelectronic with xenon?

• A. Ba^{2+}
• B. I^{-}
• C. Te^{2-}
• D. Cs^{+}

Answer: (A)

Verified step by step guidance

1. Recall that two species are isoelectronic if they have the same number of electrons.
2. Determine the number of electrons in a neutral xenon (Xe) atom. Xenon has an atomic number of 54, so it has 54 electrons.
3. Calculate the number of electrons for each ion by adjusting for their charge: - For Ba^{2+}, subtract 2 electrons from barium's atomic number (56). - For I^{-}, add 1 electron to iodine's atomic number (53). - For Te^{2-}, add 2 electrons to tellurium's atomic number (52). - For Cs^{+}, subtract 1 electron from cesium's atomic number (55).
4. Compare the electron counts of each ion to 54 (the number of electrons in xenon) to identify which ion is isoelectronic with xenon.
5. Select the ion whose electron count matches 54, confirming it is isoelectronic with xenon.