The noble gas notation is the short or abbreviated form of the electron configuration.
It means that you use the symbol of the previous noble gas as part of the electron configuration of an element.
The gas noble previous to antimony is Kr, so you do not use Xe to write the electron configuration of Sb.
The gas noble previous to radium is Rn, so you do not use Xe to wirte the electron configuration of Ra.
The gas noble previous to uranium is Rn, so you do not use Xe to write the electron configuration of U.
The gas noble previous to cesium is Xe, so you use Xe to write the noble notation for Sb. This is it: Cs: [Xe] 6s.
Answer: cesium
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