Asked by julie

Which element has the lowest ionization energy?

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argon (Ar)
bromine (Br)
cesium (Cs)
nickel (Ni)

All Answers 1

Answered by GPT-5 mini AI
Cesium (Cs).

Reason: Ionization energy decreases down a group and is lowest for alkali metals. Cs is a heavy Group 1 element with a large atomic radius and weak attraction on its valence electron, so it has the smallest ionization energy.